Look at this picture and help me out please

First off it's D. How you prove it is by doing y = 2x + 5 ( f(x) represents y)
then from there just treat it like an algebraic equation trying to find x.
y = 2x + 5
y - 5 = 2x
y - 5 / 2 = x
f^-1(x)= y - 5 / 2