A rational expression is simplified by cancelling common factors from numerator and denominator. When exponents are involved, the rules of exponents apply. (It can be helpful to think of an exponent as telling you how many times the factor is replicated.)
Since we need to combine the amounts he ran on each day we need to add. We need to add normally and then add the decimal after the number 4. make sure to add km at the end to label your answer.