How do I solve this question?

  c

Step-by-step explanation:

Work out the composition and see what you get.

This is your first clue that the functions are inverses of each other, so we expect that g(f(x)) = x will be true, too. We can work that out to confirm it.

So, the appropriate choice is as shown below.

true? is that what you're asking or do you mean something else?