Ответ:

\(\frac{1}{3}+\frac{2}{9}=\frac{3}{9}+\frac{2}{9}=\frac{5}{9}\).

\(\frac{9}{10}:\frac{5}{9}=\frac{9}{10}\cdot\frac{9}{5}=\frac{81}{50}\).

Ответ: \(\frac{81}{50}\).