15. Выполните деление: 3 1/7 : 2 2/5.

\(3\frac{1}{7}=\frac{22}{7}\), \(2\frac{2}{5}=\frac{12}{5}\).

\[\frac{22}{7}:\frac{12}{5}=\frac{22}{7}\cdot\frac{5}{12}=\frac{110}{84}=\frac{55}{42}=1\frac{13}{42}.\]

Ответ: \(1\frac{13}{42}\).