$$ \frac{50x}{10y} : \frac{x}{5y^2} \cdot \frac{25y}{5x} = \frac{50x}{10y} \cdot \frac{5y^2}{x} \cdot \frac{25y}{5x} = \frac{50x \cdot 5y^2 \cdot 25y}{10y \cdot x \cdot 5x} = \frac{6250xy^3}{50x^2y} = 125 \frac{y^2}{x} $$
Ответ: $$125 \frac{y^2}{x}$$