2) \(\frac{21}{5} \cdot \frac{3}{7} = \frac{21 \cdot 3}{5 \cdot 7} = \frac{3 \cdot 7 \cdot 3}{5 \cdot 7} = \frac{3 \cdot 3}{5} = \frac{9}{5} = 1\frac{4}{5} = 1,8\)
Ответ: \(1,8\)