diff --git a/src/project-1.js b/src/project-1.js
index dc26cfb..9982776 100644
--- a/src/project-1.js
+++ b/src/project-1.js
@@ -3,114 +3,137 @@
 const multiplyByTen = (num) => {
   // return num after multiplying it by ten
   // code here
+  return num * 10;
 };
 
 const subtractFive = (num) => {
   // return num after subtracting five
   // code here
+  return num - 5;
 };
 
 const areSameLength = (str1, str2) => {
   // return true if the two strings have the same length
   // otherwise return false
   // code here
+  return str1.length === str2.length;
 };
 
 const areEqual = (x, y) => {
   // return true if x and y are the same
   // otherwise return false
   // code here
+  return x === y;
 };
 
 const lessThanNinety = (num) => {
   // return true if num is less than ninety
   // otherwise return false
   // code here
+  return num < 90;
 };
 
 const greaterThanFifty = (num) => {
   // return true if num is greater than fifty
   // otherwise return false
   // code here
+  return num > 50;
 };
 
 const add = (x, y) => {
   // add x and y together and return the value
   // code here
+  return x + y;
 };
 
 const subtract = (x, y) => {
   // subtract y from x and return the value
   // code here
+  return x - y;
 };
 
 const divide = (x, y) => {
   // divide x by y and return the value
   // code here
+  return x / y;
 };
 
 const multiply = (x, y) => {
   // multiply x by y and return the value
   // code here
+  return x * y;
 };
 
 const getRemainder = (x, y) => {
   // return the remainder from dividing x by y
   // code here
+  return x % y;
 };
 
 const isEven = (num) => {
   // return true if num is even
   // otherwise return false
   // code here
+  return num % 2 === 0;
 };
 
 const isOdd = (num) => {
   // return true if num is odd
   // otherwise return false
   // code here
+  return num % 2 === 1;
 };
 
 const square = (num) => {
   // square num and return the new value
   // code here
+  return num * num;
 };
 
 const cube = (num) => {
   // cube num and return the new value
   // code here
+  return Math.pow(num, 3);
+  // return num * num * num;
 };
 
 const raiseToPower = (num, exponent) => {
   // raise num to whatever power is passed in as exponent
   // code here
+  return Math.pow(num, exponent);
 };
 
 const roundNumber = (num) => {
   // round num and return it
   // code here
+  return Math.round(num);
 };
 
 const roundUp = (num) => {
   // round num up and return it
   // code here
+  return Math.ceil(num);
 };
 
 const addExclamationPoint = (str) => {
   // add an exclamation point to the end of str and return the new string
   // 'hello world' -> 'hello world!'
   // code here
+  return `${str}!`;
+  // return str.concat('!');
 };
 
 const combineNames = (firstName, lastName) => {
   // return firstName and lastName combined as one string and separated by a space.
   // 'Lambda', 'School' -> 'Lambda School'
   // code here
+  return `${firstName} ${lastName}`;
 };
 
 const getGreeting = (name) => {
   // Take the name string and concatenate other strings onto it so it takes the following form:
   // 'Sam' -> 'Hello Sam!'
+  return `Hello ${name}!`;
   // code here
 };
 
@@ -119,21 +142,27 @@ const getGreeting = (name) => {
 const getRectangleArea = (length, width) => {
   // return the area of the rectangle by using length and width
   // code here
+  return length * width;
 };
 
 const getTriangleArea = (base, height) => {
   // return the area of the triangle by using base and height
   // code here
+  return (base / 2) * height;
 };
 
 const getCircleArea = (radius) => {
   // return the rounded area of the circle given the radius
   // code here
+  const res = Math.pow(radius, 2) * Math.PI;
+  return Math.round(res);
+  // return 3.14159 * radius * radius;
 };
 
 const getRectangularPrismVolume = (length, width, height) => {
   // return the volume of the 3D rectangular prism given the length, width, and height
   // code here
+  return length * width * height;
 };
 
 // Do not modify code below this line.
diff --git a/src/project-2.js b/src/project-2.js
index 5fe0047..d2ac068 100644
--- a/src/project-2.js
+++ b/src/project-2.js
@@ -3,6 +3,10 @@
 const getBiggest = (x, y) => {
   // x and y are integers.  Return the larger integer
   // if they are the same return either one
+  if (x >= y) {
+    return x;
+  }
+  return y;
 };
 
 const greeting = (language) => {
@@ -11,15 +15,43 @@ const greeting = (language) => {
   // language: 'Spanish' -> 'Hola!'
   // language: 'Chinese' -> 'Ni Hao!'
   // if language is undefined return 'Hello!'
+  if (language === 'German') {
+    return 'Guten Tag!';
+  } else if (language === 'Spanish') {
+    return 'Hola!';
+  } else if (language === 'Chinese') {
+    return 'Ni Hao!';
+  } if (language !== 'German' || language !== 'Spanish' || language !== 'Chinese') {
+    return 'Hello!';
+  }
+  // switch (language) {
+  //   case 'German':
+  //     return 'Guten Tag!';
+  //   case 'Spanish':
+  //     return 'Hola!';
+  //   case 'Chinese':
+  //     return 'Ni Hao!';
+  //   default:
+  //     return 'Hello!';
+  // }
 };
 
 const isTenOrFive = (num) => {
   // return true if num is 10 or 5
   // otherwise return false
+  if (num === 5) {
+    return true;
+  } else if (num === 10) {
+    return true;
+  } return false;
 };
 
 const isInRange = (num) => {
   // return true if num is less than 50 and greater than 20
+  // if (num < 50 && num > 20) {
+  //   return true;
+  // } return false;
+  return num < 50 && num > 20;
 };
 
 const isInteger = (num) => {
@@ -29,6 +61,18 @@ const isInteger = (num) => {
   // -10 -> true
   // otherwise return false
   // hint: you can solve this using Math.floor
+  // if (Number.isInteger(num)) return true;
+  // switch (num) {
+  //   case 0.8:
+  //     return false;
+  //   case 1:
+  //     return true;
+  //   case -10:
+  //     return true;
+  //   default:
+  //     return false;
+  // }
+  return num % 1 === 0;
 };
 
 const fizzBuzz = (num) => {
@@ -36,6 +80,15 @@ const fizzBuzz = (num) => {
   // if num is divisible by 5 return 'buzz'
   // if num is divisible by 3 & 5 return 'fizzbuzz'
   // otherwise return num
+  if (num % 3 === 0 && num % 5 === 0) {
+    return 'fizzbuzz';
+  }
+  if (num % 3 === 0) {
+    return 'fizz';
+  } else if (num % 5 === 0) {
+    return 'buzz';
+  }
+  return num;
 };
 
 const isPrime = (num) => {
@@ -44,35 +97,60 @@ const isPrime = (num) => {
   // hint: a prime number is only evenly divisible by itself and 1
   // hint2: you can solve this using a for loop
   // note: 0 and 1 are NOT considered prime numbers
+  // if (num % num === 0 && num / 1 === num) {
+  //   return true;
+  // } this passes the first test so maybe we should have it check for something else
+  if (num === 0) {
+    return false;
+  } else if (num === 1) {
+    return false;
+  } else if (num === 2) {
+    return true;
+  }
+  for (let x = 2; x < num; x++) {
+    if (num % x === 0) {
+      return false;
+    }
+  }
+  return true;
 };
 
 const returnFirst = (arr) => {
   // return the first item from the array
+  return arr[0];
 };
 
 const returnLast = (arr) => {
   // return the last item of the array
+  return arr.pop();
 };
 
 const getArrayLength = (arr) => {
   // return the length of the array
+  return arr.length;
 };
 
 const incrementByOne = (arr) => {
   // arr is an array of integers
   // increase each integer by one
   // return the array
+  return arr.map((num) => {
+    return num + 1;
+  });
 };
 
 const addItemToArray = (arr, item) => {
   // add the item to the end of the array
   // return the array
+  return arr.concat(item);
 };
 
 const addItemToFront = (arr, item) => {
   // add the item to the front of the array
   // return the array
   // hint: use the array method .unshift
+  arr.unshift(item);
+  return arr;
 };
 
 const wordsToSentence = (words) => {
@@ -80,26 +158,41 @@ const wordsToSentence = (words) => {
   // return a string that is all of the words concatenated together
   // spaces need to be between each word
   // example: ['Hello', 'world!'] -> 'Hello world!'
+  return words.join(' ');
 };
 
 const contains = (arr, item) => {
   // check to see if item is inside of arr
   // return true if it is, otherwise return false
+  return arr.includes(item);
 };
 
 const addNumbers = (numbers) => {
   // numbers is an array of integers.
   // add all of the integers and return the value
+  return numbers.reduce((x, y) => {
+    return x + y;
+  });
 };
 
 const averageTestScore = (testScores) => {
   // testScores is an array.  Iterate over testScores and compute the average.
   // return the average
+  let temp = 0;
+  temp = testScores.reduce((a, b) => {
+    return a + b;
+  });
+  return temp / testScores.length;
 };
 
 const largestNumber = (numbers) => {
   // numbers is an array of integers
   // return the largest integer
+  // numbers.sort((a, b) => {
+  //   return b > a;
+  // });
+  // return numbers[0];
+  return Math.max(...numbers);
 };
 
 // Do not modify code below this line.
diff --git a/src/project-3.js b/src/project-3.js
index 7ca1430..b6a7470 100644
--- a/src/project-3.js
+++ b/src/project-3.js
@@ -5,61 +5,114 @@ const makeCat = (name, age) => {
   // add an age property to the object with the value set to the age argument
   // add a method called meow that returns the string 'Meow!'
   // return the object
+  const cat = {
+    name,
+    age,
+    meow: () => {
+      return 'Meow!';
+    }
+  };
+  return cat;
 };
 
 const addProperty = (object, property) => {
   // add the property to the object with a value of null
   // return the object
   // note: the property name is NOT 'property'.  The name is the value of the argument called property (a string)
+  object[`${property}`] = null;
+  return object;
 };
 
+
 const invokeMethod = (object, method) => {
   // method is a string that contains the name of a method on the object
   // invoke this method
   // nothing needs to be returned
+  return object[method]();
 };
+// const obj = {
+//   x: 1,
+//   y: () => {
+//     console.log('woof!');
+//   }
+// };
+// console.log(invokeMethod(obj, 'y'));
 
 const multiplyMysteryNumberByFive = (mysteryNumberObject) => {
   // mysteryNumberObject has a property called mysteryNumber
   // multiply the mysteryNumber property by 5 and return the product
+  return mysteryNumberObject.mysteryNumber * 5;
 };
 
+// const mysteryBox = {
+//   mysteryNumber: 999
+// };
+// console.log(multiplyMysteryNumberByFive(mysteryBox));
+
 const deleteProperty = (object, property) => {
   // remove the property from the object
   // return the object
+  delete object[property];
+  return object;
 };
 
 const newUser = (name, email, password) => {
   // create a new object with properties matching the arguments passed in.
   // return the new object
+  return {
+    name: `${name}`,
+    email: `${email}`,
+    password: `${password}`
+  };
 };
 
 const hasEmail = (user) => {
   // return true if the user has a value for the property 'email'
   // otherwise return false
+  const check = user.email;
+  // console.log(check);
+  if (check !== undefined && check.length > 1) {
+    return true;
+  }
+  return false;
 };
 
+
 const hasProperty = (object, property) => {
   // return true if the object has the value of the property argument
   // property is a string
   // otherwise return false
+  const check = Object.keys(object);
+  if (check.includes(property)) {
+    return true;
+  }
+  return false;
 };
 
 const verifyPassword = (user, password) => {
   // check to see if the provided password matches the password property on the user object
   // return true if they match
   // otherwise return false
+  return (user.password === password);
 };
 
+
 const updatePassword = (user, newPassword) => {
   // replace the existing password on the user object with the value of newPassword
   // return the object
+  user.password = newPassword;
+  return user;
 };
 
+const obj = { username: 'SunJieMing', email: '', password: 'I love js!' };
+
+// console.log(updatePassword(obj, 'ok'));
 const addFriend = (user, newFriend) => {
   // user has a property called friends that is an array
   // add newFriend to the end of the friends array
   // return the user object
+  user.friends.push(newFriend);
+  return user;
 };
 
 const setUsersToPremium = (users) => {
@@ -67,6 +120,15 @@ const setUsersToPremium = (users) => {
   // each user object has the property 'isPremium'
   // set each user's isPremium property to true
   // return the users array
+  // return users.map((user) => {
+    //   user.isPremium = true;
+    // console.log(ob);
+    // console.log(users);
+    // });
+  users.forEach((ob) => {
+    return ob.isPremium = true;
+  });
+  return users;
 };
 
 const sumUserPostLikes = (user) => {
@@ -75,6 +137,17 @@ const sumUserPostLikes = (user) => {
   // each post object has an integer property called 'likes'
   // sum together the likes from all the post objects
   // return the sum
+  // user.forEach((post) => {
+  //   console.log(user);
+  //   return post.map((ob) => {
+  //     return ob.likes += ob.likes;
+  //   });
+  // });
+  let totalLikes = 0;
+  user.posts.map((ob) => {
+    return totalLikes += ob.likes;
+  });
+  return totalLikes;
 };
 
 const addCalculateDiscountPriceMethod = (storeItem) => {
@@ -87,8 +160,21 @@ const addCalculateDiscountPriceMethod = (storeItem) => {
   // discountPrice = 20 - (20 * .2)
   // Make sure you return storeItem after adding the method to it
   // hint: arrow functions don't bind a this
+  // let discountPrice = 0;
+  storeItem.calculateDiscountPrice = () => {
+    return storeItem.price - (storeItem.price * storeItem.discountPercentage);
+  };
+  return storeItem;
 };
-
+const storeItem = {
+  price: 80,
+  discountPercentage: 0.1
+};
+const storeItem2 = {
+  price: 5,
+  discountPercentage: 0.5
+};
+console.log(addCalculateDiscountPriceMethod(storeItem2));
 // Do not modify code below this line.
 // --------------------------------
 
diff --git a/src/project-4.js b/src/project-4.js
index 3a3a186..1d945f5 100644
--- a/src/project-4.js
+++ b/src/project-4.js
@@ -1,32 +1,61 @@
 const getFirstItem = (collection, cb) => {
   // invoke the callback function and pass the first item from the collection in as an argument
+  cb(collection[0]);
 };
 
 const getLength = (collection, cb) => {
   // Write a function called getLength that passes the length of the array into the callback
+  cb(collection.length);
 };
 
 const getLastItem = (collection, cb) => {
   // Write a function called getLastItem which passes the getLastItem item of the array into the callback
+  cb(collection.pop());
 };
 
 const sumNums = (x, y, cb) => {
   // Write a function called sumNums that adds two numbers and passes the result to the callback
+  cb(x + y);
 };
 
 const multiplyNums = (x, y, cb) => {
   // Write a function called multiplyNums that multiplies two numbers and passes the result to the callback
+  const result = x * y;
+  cb(result);
 };
 
 const contains = (collection, item, cb) => {
   // Write a function called contains that checks if an item is present inside of the given array.
   // Pass true to the callback if it is, otherwise pass false
+  let results = false;
+  if (collection.includes(item)) {
+    results = true;
+  }
+  cb(results);
 };
 
+// const animals = ['ant', 'bison', 'camel', 'duck', 'elephant', 'duck', 'elephant'];
+// const arr = ['a', 'b', 'c', 'c'];
+
 const removeDuplicates = (collection, cb) => {
   // Write a function called removeDuplicates that removes all duplicate values from the given array.
   // Pass the array to the callback function.  Do not mutate the original array.
+  const newArr = [...collection].sort((a, b) => {
+    return a > b;
+  });
+  for (let i = 0; i < newArr.length; i++) {
+    if (newArr[i] === newArr[i + 1]) {
+      newArr.splice(i, 1);
+    }
+  }
+  cb(newArr);
 };
+// removeDuplicates(animals, function(x) {
+//   console.log(x);
+// });
+// removeDuplicates(arr, function(x) {
+//   console.log(x);
+// });
 
 module.exports = {
   getFirstItem,