The first thing you should do in this case is to compose both functions: f (x) = x + 7 g (x) = 1 / (x-13) Making the composition f (g (x)) = (1 / (x-13)) + 7 f (g (x)) = (7 (x-13) +1) / (x-13) Answer: The domain of the function is: x other than 13 (option 4)