3. \(\frac{4}{7} \cdot \frac{14}{20}\)

Сократим дроби: \(14:7=2\), \(4:20=1:5\).

\(\frac{4}{7}\cdot\frac{14}{20}=\frac{1\cdot2}{1\cdot5}=\frac{2}{5}\).

Ответ: \(\frac{2}{5}\).