1. Сократите дроби: 28/35; 8/12; 39/12; (9×14)/(28×3).

1. \(\frac{28}{35}=\frac{28\div7}{35\div7}=\frac45\).
2. \(\frac8{12}=\frac{8\div4}{12\div4}=\frac23\).
3. \(\frac{39}{12}=\frac{39\div3}{12\div3}=\frac{13}4\).
4. \(\frac{9\times14}{28\times3}=\frac{126}{84}=\frac32\).

Ответ: \(\frac45;\ \frac23;\ \frac{13}4;\ \frac32\).