Решение:

1) $$rac{x}{y-1} + \frac{2}{1-y} = \frac{x}{y-1} - \frac{2}{y-1} = \frac{x-2}{y-1}$$ 2) $$rac{3c}{c-d} + \frac{3d}{d-c} = \frac{3c}{c-d} - \frac{3d}{c-d} = \frac{3c-3d}{c-d} = \frac{3(c-d)}{c-d} = 3$$ 3) $$rac{3m+2n}{2m-3n} - \frac{m-8n}{3n-2m} = \frac{3m+2n}{2m-3n} + \frac{m-8n}{2m-3n} = \frac{3m+2n+m-8n}{2m-3n} = \frac{4m-6n}{2m-3n} = \frac{2(2m-3n)}{2m-3n} = 2$$ 4) $$rac{b^2}{2b-14} + \frac{49}{14-2b} = \frac{b^2}{2(b-7)} - \frac{49}{2(b-7)} = \frac{b^2-49}{2(b-7)} = \frac{(b-7)(b+7)}{2(b-7)} = \frac{b+7}{2}$$