368. Выполните действия: а) \(\left(\frac{5}{8}-\frac{2}{5}\right)+\frac{3}{20}\); б) \(\frac{5}{6}-\left(\frac{3}{10}+\frac{2}{5}\right)\).

а)

\[\left(\frac{5}{8}-\frac{2}{5}\right)+\frac{3}{20}=\left(\frac{25}{40}-\frac{16}{40}\right)+\frac{6}{40}=\frac{15}{40}=\frac{3}{8}.\]

б)

\[\frac{5}{6}-\left(\frac{3}{10}+\frac{2}{5}\right)=\frac{5}{6}-\left(\frac{3}{10}+\frac{4}{10}\right)=\frac{5}{6}-\frac{7}{10}=\frac{25}{30}-\frac{21}{30}=\frac{2}{15}.\]

Ответ: а) \(\frac{3}{8}\); б) \(\frac{2}{15}\).