(47−712)+12 equals
40
We know that (x−y)+z=x−(y−z), for all numbers x, y, z with y>z.
Since the above is true for all the numbers, it must be true for x=47, y=712 and z=12 also, as y=712>12=z
So, (47−712)+12 = 47−(712−12) = 47−(152−12) = 47−7 = 40