4/7 : 8/21 = ?

$$\frac{4}{7} : \frac{8}{21} = \frac{4}{7} \cdot \frac{21}{8} = \frac{4 \cdot 21}{7 \cdot 8} = \frac{4 \cdot 3 \cdot 7}{7 \cdot 4 \cdot 2} = \frac{3}{2} = 1\frac{1}{2}$$

Ответ: 1 1/2