18. \(\frac{21}{32}\cdot\frac{16}{35}=\)

Сократим: \(\frac{21}{35}=\frac{3}{5}\), \(\frac{16}{32}=\frac{1}{2}\).

\(\frac{21}{32}\cdot\frac{16}{35}=\frac{3}{5}\cdot\frac{1}{2}=\frac{3}{10}\).

Ответ: \(\frac{3}{10}\)