в) $$\frac{9}{8} : \frac{5}{8} \cdot \frac{3}{10} = \frac{9}{8} \cdot \frac{8}{5} \cdot \frac{3}{10} = \frac{9 \cdot 8 \cdot 3}{8 \cdot 5 \cdot 10} = \frac{9 \cdot 3}{5 \cdot 10} = \frac{27}{50}$$.
Ответ: $$\frac{27}{50}$$