The original function is f(x) = 4x - 12...
to find the inverse function, we need to solve it for x:
f(x) = 4x - 12
f(x) + 12 = 4x
(f(x) + 12)/ 4 = x
f(x)/4 + 3 = x
if we change now f^-1(x) for x and x for f^-1(x):
x/4 + 3 = f^-1(x)
f^-1(x) = x/4 + 3
f^-1(x) = (1/4)x + 3
Answer: