Clarified ambiguous instructions

02-functions/practice.js

@@ -1,10 +1,9 @@
-// (example) Write a function that accepts two number arguments and adds them
-// together.
+// Write a function that accepts two number arguments and returns their sum
 var add = function () {
 };
 
 
-// Create a function that takes in a cost and a quantity and outputs the total
+// Create a function that takes in a cost and a quantity and returns the total
 // pre-tax cost for that quantity of items at the given price. For example
 //
 //     var preTaxTotal = totalCost(5, 5.99); // 5 items at 5.99

05-loops/practice.js

@@ -154,7 +154,7 @@ var isPrime = function () {
 
 
 // Using the `isPrime` function, write a function that accepts a number as
-// input sums all the primes smaller than that number.
+// input sums all the primes smaller or equal to that number.
 //
 //     sumPrimesUpTo(100);
 //     //=> 1060
@@ -176,7 +176,7 @@ var sumPrimesUpTo = function () {
 
 
 // Using the `isPrime` function, write a function that takes in a
-// positive integer, n, and returns the first n numbers.
+// positive integer, n, and returns the sum of the first n prime numbers.
 //
 //     sumOfFirstNPrimes(10);
 //     //=> 129
@@ -214,7 +214,7 @@ var sumOfFirstNPrimes = function () {
 //      //=> false
 //
 // Let's start by writing a function to remove all non-letter characters
-// from the input.
+// from the input. If the input is not a string, throw an error.
 //
 //     removeNonLetters("A man, a plan, a canal, Panama");
 //     //=> AmanaplanacanalPanama

06-arrays/practice.js

@@ -1,5 +1,5 @@
-// Write a function called `containsTwice` that accepts a number and an array,
-// and returns `true` if that number appears in the array twice, and `false`
+// Write a function called `containsTwice` that accepts an element and an array,
+// and returns `true` if that element appears in the array twice, and `false`
 // otherwise.
 //
 //     containsTwice(5, [1, 2, 3, 4, 5]);
@@ -103,7 +103,8 @@ var containsAnyTwice = function () {
 // In the previous problem, we determined whether or not an array contains any
 // of a list of values exactly twice. In this problem, we'll actually return
 // those values appearing twice.  Create a new function that returns an array of
-// only the values from the first array that appear twice in the second array.
+// only the values that appear twice in the array.
+//
 //
 // For this problem, you'll create a new array, and you'll use its `push`
 // function to add elements to the end. You'll most likely want to use the