15) $$rac{15b}{8} \cdot \frac{2}{35b} =$$

$$\frac{15b}{8} \cdot \frac{2}{35b} = \frac{15b \cdot 2}{8 \cdot 35b} = \frac{30b}{280b} = \frac{30}{280} = \frac{3}{28}$$ Ответ: $$\frac{3}{28}$$