Finding the inverse of a function?

Question

lets say I have the function f(x)=5x+8

how do i use algebra to find the inverse of the function. i know f(g(x)) has to equal x so what it the g(x) (inverse) of f(x)=5x+8.

what steps do i need to take

Answer 1

switch the x's and y's

x=5y+8
5y=x-8
y=(x-8)/5

Answer 2

f(x) = 5x + 8
Inverse is function , g such that :-
g(5x + 8) = x
Let u = 5x + 8 so x = (1/5).(u - 8)
g(u) = (1/5).(u - 8)
This may be written as :-
g(x) = (1/5). (x - 8)