\[\frac{3xy - y^{2}}{xy + 2y^{2}} \cdot \frac{x^{2}y + 2xy^{2}}{3x^{3} - x^{2}y} =\]
\[= \frac{y(3x - y) \cdot xy(x + 2y)}{y(x + 2y) \cdot x²(3x - y)} = \frac{y}{x}\]