This is an impossible equation. You can tell by intuition, becuase you're asking a quantity (4x) to equal the same quantity minus 3.
The question sounds like: "which number is equal to itself minus 3?" which should make clear why it is an impossible question.
Anyway, if we want to perform the proper math, we can simply go like this: starting with
Subtract 4x from both sides:
which, again, is an impossible equation.