diff --git a/src/main/java/tdd/setup/Calculator.java b/src/main/java/tdd/setup/Calculator.java
index 171f6d6..1c73b55 100644
--- a/src/main/java/tdd/setup/Calculator.java
+++ b/src/main/java/tdd/setup/Calculator.java
@@ -14,8 +14,8 @@ public String readScreen() {
     }
     public void pressDigitKey(int digit) {
         if(digit > 9 || digit < 0) throw new IllegalArgumentException();
-
-        if(latestOperation.isEmpty()) {
+        //bug fix for two tests (multi-digits and double number)
+        if(latestOperation.isEmpty() || latestValue != 0.0) {
             screen = screen + digit;
         } else {
             latestValue = Double.parseDouble(screen);
@@ -47,6 +47,7 @@ public void pressEquals() {
             case "-" -> latestValue - Double.parseDouble(screen);
             case "x" -> latestValue * Double.parseDouble(screen);
             case "/" -> latestValue / Double.parseDouble(screen);
+            case "1/x" -> 1/ Double.parseDouble(screen); //function "1/x"
             default -> throw new IllegalArgumentException();
         };
         screen = Double.toString(result);
diff --git a/src/test/java/tdd/setup/CalculatorTest.java b/src/test/java/tdd/setup/CalculatorTest.java
index 3bf16e9..f8cae73 100644
--- a/src/test/java/tdd/setup/CalculatorTest.java
+++ b/src/test/java/tdd/setup/CalculatorTest.java
@@ -16,4 +16,52 @@ void calculatorCanDoTwoPlusTwo() {
         calc.pressEquals();
         assertEquals("4", calc.readScreen());
     }
+
+    @Test
+    @DisplayName("should display result after multiplying positive and negative numbers")
+    void calculatorCanDoEightTimesNegativeTwo() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(8);
+        calc.pressOperationKey("x");
+        calc.pressNegative();
+        calc.pressDigitKey(2);
+        calc.pressEquals();
+        assertEquals("-16", calc.readScreen());
+    }
+
+    @Test
+    @DisplayName("should display result after multiplying integer and double numbers")
+    void calculatorCanDoEightTimesTwoDotTwo() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(8);
+        calc.pressOperationKey("x");
+        calc.pressDigitKey(2);
+        calc.pressDotKey();
+        calc.pressDigitKey(2);
+        calc.pressEquals();
+        assertEquals("17.6", calc.readScreen());
+    }
+
+    @Test
+    @DisplayName("should display result after multiplying integer numbers and multi-digit")
+    void calculatorCanDoEightTimesTwentyTwo() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(8);
+        calc.pressOperationKey("x");
+        calc.pressNegative();
+        calc.pressDigitKey(2);
+        calc.pressDigitKey(2);
+        calc.pressEquals();
+        assertEquals("-176", calc.readScreen());
+    }
+
+    @Test
+    @DisplayName("should display result after one divided with integer")
+    void calculatorCanDoOneFourth() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(4);
+        calc.pressOperationKey("1/x");
+        calc.pressEquals();
+        assertEquals("0.25", calc.readScreen());
+    }
 }