Answer :
Basically you swap the variables.
f(x)=4x-12
y = 4x - 12
SWAP
x = 4y - 12
Now solve for y
X = 4y - 12
x + 12 = 4y
X/4 + 3 = y
The inverse is y = x/4 + 3
f(x)=4x-12
y = 4x - 12
SWAP
x = 4y - 12
Now solve for y
X = 4y - 12
x + 12 = 4y
X/4 + 3 = y
The inverse is y = x/4 + 3