a) $$\frac{2}{4 \cdot 15}: \frac{5}{3 \cdot 9} = \frac{2}{60}:\frac{5}{27} = \frac{2}{60} \cdot \frac{27}{5} = \frac{2 \cdot 27}{60 \cdot 5} = \frac{54}{300} = \frac{27}{150} = \frac{9}{50}$$
Ответ: $$\frac{9}{50}$$
б) $$\frac{3}{131} : \frac{8}{52} = \frac{3}{131} : \frac{2 \cdot 4}{13 \cdot 4} = \frac{3}{131} \cdot \frac{13 \cdot 4}{2 \cdot 4} = \frac{3 \cdot 13}{131 \cdot 2} = \frac{39}{262}$$
Ответ: $$\frac{39}{262}$$