f(x) = 3x - 1/2
is the inverse of f(x). Let y = f(x)
y = 3x - 1/2
To find the inverse function, replace y with x and x with y
x = 3y - 1/2
After solving and simplifying the equation for y, you will get the following equation
y = x/3 + 1/6
This is the inverse of f(x). Now, substitute x = 4
y = 4/3 + 1/6
= 8/6 + 1/6
= 9/6
= 3/2
That should be your answer. Let me know if you need any clarifications, thanks!