\[\left( \frac{5}{2x - 4y} - \frac{1}{2y - x} \right)\ :\frac{3}{x - 2y} =\]
\[= \frac{5 - 2}{2 \bullet (x - 2y)}\ :\frac{3}{x - 2y} =\]
\[Ответ:\frac{1}{2}.\]