Сократите дробь: г) $$\frac{7ab}{21bc}$$

$$\frac{7ab}{21bc} = \frac{7}{21} \cdot \frac{a}{1} \cdot \frac{b}{b} \cdot \frac{1}{c} = \frac{1}{3} \cdot a \cdot 1 \cdot \frac{1}{c} = \frac{a}{3c}$$