1. Сократите дроби: 6/8; 15/25; 10/40; 21/28.

1. \(\frac{6}{8}=\frac{6:2}{8:2}=\frac{3}{4}\).
2. \(\frac{15}{25}=\frac{15:5}{25:5}=\frac{3}{5}\).
3. \(\frac{10}{40}=\frac{10:10}{40:10}=\frac{1}{4}\).
4. \(\frac{21}{28}=\frac{21:7}{28:7}=\frac{3}{4}\).

Ответ: \(\frac{3}{4};\ \frac{3}{5};\ \frac{1}{4};\ \frac{3}{4}\).