Сокращение дробей

1. a) $$rac{21a^3b}{35a^4b} = \frac{3}{5a}$$
2. b) $$rac{4x^2-20x}{10x} = \frac{4x(x-5)}{10x} = \frac{2(x-5)}{5}$$
3. c) $$\frac{x^2-49}{2x+14} = \frac{(x-7)(x+7)}{2(x+7)} = \frac{x-7}{2}$$