public void exercise9(double firstNumber, double secondNumber, double thridNumber, string expected)
        {
            // Dado / Setup
            var exercises = new Exercises1();
            // 1, 4 , 12.5

            // Quando / Ação
            string returnedValues = exercises.Exercise9(firstNumber, secondNumber, thridNumber);

            // Deve / Asserções
            Assert.Equal(expected, returnedValues);
        }