\[\frac{2xy^{2}}{3x - y}\ :\frac{xy^{3}}{9x^{2} - y^{2}} \cdot \frac{2y}{3x + y} =\]
\[= \frac{2xy^{2}(3x - y)(3x + y) \cdot 2y}{(3x - y)xy^{3}(3x + y)} = 4.\]