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);
}