Answer
$23 x^{2}y-4 x^{3} y^{2}-8 x^{2} y^{2}-9 x y^{2}$
Work Step by Step
This problem deals with combining like terms. Like terms are terms that have the same variable raised to the same power. Recall, if terms are like terms, we can add or subtract these terms just like we add or subtract numbers. Because 12$x^{2}y$ and 11$x^{2}y$ are like terms, we can add them to simplify the expression to:
$23 x^{2}y-4 x^{3} y^{2}-8 x^{2} y^{2}-9 x y^{2}$
