Решение:

$$\frac{10x^2y^4(c-d)}{20xy^5(d-c)} = \frac{x(c-d)}{2y(d-c)} = \frac{x(-1)(d-c)}{2y(d-c)} = -\frac{x}{2y}$$

Ответ: $$\frac{-x}{2y}$$