Answer :
I assume you meant to type x for %.
If not, basically back-substitute at the end of the solution.
F(x) = 4x - 3
Let y = F(x)
y = 4x - 3
x = 4y - 3
x - 3 = 4y
(x - 3)/4 = y
Let y = F^(-1)x
F^(-1)x = (x - 3)/4
If you want % in your answer, just replace x for % in your answer.