1. Сократи: 9/15, 8/56, 42/90.

1. \(\frac{9}{15}=\frac{9:3}{15:3}=\frac{3}{5}\).
2. \(\frac{8}{56}=\frac{8:8}{56:8}=\frac{1}{7}\).
3. \(\frac{42}{90}=\frac{42:6}{90:6}=\frac{7}{15}\).

Ответ: \(\frac{3}{5},\ \frac{1}{7},\ \frac{7}{15}\).