The original transformation (2x, y+5) takes any x value and doubles it. So the inverse of this is to cut the x value in half. We can say x/2 since division is the opposite of multiplication. The value x/2 is the same as ½x
For the y coordinate, we add on 5 for the original transformation. Subtraction undoes addition meaning the inverse will have y-5.
Side note: the inverse notation can be written as T^(-1).