г) (5-y)/2y * 3y²/(y²-25)

г) $$\frac{5-y}{2y} \cdot \frac{3y^2}{y^2-25} = \frac{-(y-5)}{2y} \cdot \frac{3y^2}{(y-5)(y+5)} = -\frac{3y}{2(y+5)}$$

Ответ: (-3y)/(2(y+5))