What is the inverse of the functiob f(x)=1/4x-12

Replace the f(x) with y and proceed to make x the subject:
y=1/4x-12
y+12=1/4x
To ÷1/4 on both sides, ×4 on both sides
4(y+12)=x
4y+48=x
Now swap y with x and replace the isolated x with f(x) to get the inverse function: