==> 7 cows minus 4 cows = 3 cows .
==> 7 rocks minus 4 rocks = 3 rocks
==> 7 of anything minus 4 of the same thing = 3 of them
==> 7 times (the sum of "a" squared and "b")
minus
4 times (the sum of "a" squared and "b")
leaves
3 times (the sum of "a" squared and "b")
