3. 5 1) (3 - (x+y)/(x-y)) : (3x/(x+y) - 2);

1) $$(3 - \frac{x+y}{x-y}) : (\frac{3x}{x+y} - 2) = \frac{3(x-y) - (x+y)}{x-y} : \frac{3x - 2(x+y)}{x+y} = \frac{3x - 3y - x - y}{x-y} : \frac{3x - 2x - 2y}{x+y} = \frac{2x - 4y}{x-y} : \frac{x - 2y}{x+y} = \frac{2(x-2y)}{x-y} \cdot \frac{x+y}{x-2y} = \frac{2(x-2y)(x+y)}{(x-y)(x-2y)} = \frac{2(x+y)}{x-y}$$.

Ответ: $$\frac{2(x+y)}{x-y}$$