Here's the problem that my friends and I are struggling with. We have 55 summer questions to do and we're stumped on these. Could anyone help?

(I don't know how to write exponents within this text, so I used words - I hope it is clear.)

There are two expressions. Answer a)., b)., and c). for each expression.

Expression #1) f(x) = (x-3)/(x+5)

Expression #2) f(x) = 3(2 to the x power)

Question a). Find (f to the negative 1st power)(x)

Question b). Compute (f of f to the negative 1st power)(x)

Question c). Compute (f to the negative 1st power of f)(x)

Thanks to anyone who can help.