The original transformation T takes some point (x,y) and turns it into (2x, y+5). What's going on with the coordinates? Well x is doubled to 2x while y is having 5 added to it. To get the inverse, we simply undo everything happening to the coordinates. We do the opposite.
Going from x to 2x has us multiply by 2. To backwards, we divide by 2. This is the same as multiplying by 1/2. At this point, the only answer is B. So we could stop here if we wanted. But let's keep going.
To go from y to y+5, we add on 5. Undo this by subtracting 5. So the inverse would be y-5.
That's why the inverse transformation is (1/2x, y-5)
