Ответ:

а) \(3\frac{8}{13}-\frac{5}{13}=3\frac{3}{13}=3\frac{9}{39}\). Скобки: \(1\frac{5}{39}-\frac{1}{13}=1\frac{5}{39}-\frac{3}{39}=1\frac{2}{39}\). Тогда \(3\frac{9}{39}+1\frac{2}{39}=4\frac{11}{39}\).

б) \(1\frac{2}{3}-\frac{1}{6}=\frac{5}{3}-\frac{1}{6}=\frac{3}{2}\); \(\left(\frac{3}{2}\right)^2\cdot\frac{7}{3}:\frac{5}{6}=\frac{9}{4}\cdot\frac{7}{3}\cdot\frac{6}{5}=\frac{63}{10}=6\frac{3}{10}\).

Ответ: а) \(4\frac{11}{39}\); б) \(6\frac{3}{10}\).