Do you know the general procedure? What ideas have you had so far?
So what, exactly have you done? Did you get to ?
Do you know that the inverse to is ln(x)?
Here's another way of looking at it: basically tells you to do two things to x to evaluate the function: first take the exponential, then subtract 4. To find the inverse do the opposite things in the opposite order. Since the last thing you do in evaluating the function is "subtract 4", the first thing you do in finding the inverse is "add 4". Since the first thing you do in evaluating the function is take the exponential, the last ting you do in finding the inverse is the opposite of that. What function is the inverse to again?