Suppose f(x) is an invertible function, and suppose that f(2)=f^{-1}(2)=4. What is the value of f(f(2))?

We know that f (2) = 4

So f(f(2)) = f(4)

If f^{-1}(2) = 4 then f(4) = 2

So

f(f(2)) = f(4) = 2