5) \(\frac{18}{35}\cdot\frac{5}{21}:\frac{36}{49}=\)

\[\frac{18}{35}\cdot\frac{5}{21}:\frac{36}{49}=\frac{18}{35}\cdot\frac{5}{21}\cdot\frac{49}{36}\]

Сократим множители:

\[\frac{1}{7}\cdot\frac{5}{21}\cdot\frac{49}{2}=\frac{5}{6}\]

Ответ: \(\frac{5}{6}\).