38 = 7 21

$$\frac{3}{7} : \frac{8}{21} = \frac{3}{7} \cdot \frac{21}{8} = \frac{3 \cdot 21}{7 \cdot 8} = \frac{3 \cdot 3 \cdot 7}{7 \cdot 8} = \frac{9}{8} = 1\frac{1}{8}$$

Ответ: 1 1/8