4) Вычислите: \(\frac{5}{9}:\left(\frac{7}{9}+\frac{11}{18}\right)\).

\[\frac{5}{9}:\left(\frac{7}{9}+\frac{11}{18}\right)=\frac{5}{9}:\left(\frac{14}{18}+\frac{11}{18}\right)=\frac{5}{9}:\frac{25}{18}=\frac{5}{9}\cdot\frac{18}{25}=\frac{2}{5}.\]

Ответ: \(\frac{2}{5}\).