a) $$3\frac{1}{8} \cdot 5 = \frac{25}{8} \cdot 5 = \frac{125}{8} = 15\frac{5}{8} = 15.625$$
б) $$7 \cdot 2\frac{3}{7} = 7 \cdot (2 + \frac{3}{7}) = 7 \cdot 2 + 7 \cdot \frac{3}{7} = 14 + 3 = 17$$
в) $$2\frac{2}{5} \cdot 10 = \frac{12}{5} \cdot 10 = \frac{120}{5} = 24$$
Ответ: a) $$15\frac{5}{8}$$; б) 17; в) 24