(12+213)−13 equals
14
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=12, y=213 and z=13 also, as y=213>13=z
So, (12+213)−13 = 12+(213−13) = 12+(73−13) = 12+2 = 14