The answer is 5. The question wants you to compose the functions to get g(x) composed of f(x). Typically, when composing functions your substitute the second function into the first function in place of x. However, the function g(x) is constant at 5 since it has no x values. g(x)=5 means that g(x) is 5 at all values of x. Thus, in this case, it doesn't matter that we are doing a composition because the top-level function is g(x) and g(x) is 5 no matter what.