Since the 85 dollar fee is fixed, there should be no coefficient or constant that accompanies it. However, the total cost of the miles is directly proportional to the number of miles he drives. Thus, 0.35 should be accompanied by a constant that represents the total number of miles he drove. In this case, that constant is and will represent the cost from the number of miles he drives in addition to the 85$ flat fee, hence
function composition is an operation that takes two functions f and g and produces a function h such that h(x) = g(f(x)). In this operation, the function g is applied to the result of applying the function f to x.
