What's the inverse function of f^(-1)=(x-12)/3

Question

I really can't figure it out. :

Answer 1

f^-1 = (x-12)/3

Inverse of given function is (f^-1)^-1(x) = f(x)

[We know that in given function 3 is in division property and 12 is in subtraction property but in inverse function 3 is in multiplication property and 12 is in addition property.] 

(f^-1)^-1 = 3x+12

To check: f^-1(f(x)) = f(f^-1(x)) = x

f^-1(f(x)) = f^-1(3x+12)

= (3x+12-12)/3

= 3x/3

= x

f(f^-1(x)) = (x-12)/3

= (3(x-12)/3)+12

= x-12+12

= x

Inverse function of given function is 3x+12