247. Сократите дроби: 4/6, 15/12, 70a/140a, 35n/21n.

1. \(\frac{4}{6}=\frac{4:2}{6:2}=\frac{2}{3}\).
2. \(\frac{15}{12}=\frac{15:3}{12:3}=\frac{5}{4}\).
3. При \(a\ne0\): \(\frac{70a}{140a}=\frac{70}{140}=\frac{1}{2}\).
4. При \(n\ne0\): \(\frac{35n}{21n}=\frac{35}{21}=\frac{5}{3}\).

Ответ: \(\frac{2}{3};\ \frac{5}{4};\ \frac{1}{2};\ \frac{5}{3}\).