39. Вычислите: \(\frac{7}{13}+3\frac{3}{13}\cdot\left(\frac{2}{21}-\frac{3}{28}\right)-\frac{1}{5}\).

\[\frac{2}{21}-\frac{3}{28}=\frac{8-9}{84}=-\frac{1}{84}.\]

\[3\frac{3}{13}\cdot\left(-\frac{1}{84}\right)=\frac{42}{13}\cdot\left(-\frac{1}{84}\right)=-\frac{1}{26}.\]

\[\frac{7}{13}-\frac{1}{26}-\frac{1}{5}=\frac{14-1}{26}-\frac{1}{5}=\frac{13}{26}-\frac{1}{5}=\frac{1}{2}-\frac{1}{5}=\frac{3}{10}.\]

Ответ: \(\frac{3}{10}\).