447)
$\big(-\frac{5}{2}xy^2-\frac{1}{2}xy^2\big)+\frac{2}{3}x^2y-\big(x^2y-\frac{2}{3}xy^2\big)-\big(-\frac{1}{3}xy^2-\frac{1}{3}x^2y\big)+2xy^2$ =
= $-3xy^2+\frac{2}{3}x^2y-x^2y+\frac{2}{3}xy^2+\frac{1}{3}xy^2+\frac{1}{3}x^2y+2xy^2$ =
=$-xy^2+x^2y-x^2y+xy^2$ =
= $0$