How much bigger is 15x^{2}y^{2}^{ }– 18xy^{2} – 10x^{2}y than -5x^{2} + 6x^{2}y – 7xy ?
The required result,
(5x^{2}y^{2} – 18xy^{2} – 10x^{2}y) – (-5x^{2 }+ 6x^{2}y – 7xy)
= 5x^{2}y^{2} – 18xy^{2} – 10x^{2}y + 5x^{2} – 6x^{2}y + 7xy
= 5x^{2}y^{2} – 18xy^{2 }– 16x^{2}y + 5x^{2 }+ 7xy