Add tests and code for divide function

CalculatorLibrary/calculator.py

@@ -13,3 +13,7 @@ def subtract(first_term, second_term):
 
 def multiply(first_term, second_term):
     return first_term * second_term
+
+
+def divide(first_term, second_term):
+    return first_term / second_term

CalculatorLibrary/test_calculator.py

@@ -15,3 +15,6 @@ class TestCalculator:
 
     def test_multiplication(self):
         assert 100 == calculator.multiply(10, 10)
+
+    def test_divide(self):
+        assert 20 == calculator.divide(100, 5)