What is f^-1f^-1(4)

Question

What is the Composite mapping of the following question

Answer 1

f^-1(x) = f(x)

f^-1(x) is the inverse of f(x),

and f(x) is the inverse of f^-1(x)

f^-1(f^-1(x)) = f^-1(f(x)) = x

replace x with 4