а) 3 8/13 − 5/13 + (1 5/39 − 1/13); б) (1 2/3 − 1/6)^2 · 2 1/3 : 5/6.

а) \(3\frac{8}{13}-\frac{5}{13}=3\frac{3}{13}=\frac{42}{13}\).

\(1\frac{5}{39}-\frac{1}{13}=1\frac{5}{39}-\frac{3}{39}=1\frac{2}{39}=\frac{41}{39}\).

\(\frac{42}{13}+\frac{41}{39}=\frac{126}{39}+\frac{41}{39}=\frac{167}{39}=4\frac{11}{39}\).

б) \(1\frac{2}{3}-\frac{1}{6}=\frac{10}{6}-\frac{1}{6}=\frac{3}{2}\).

\(\left(\frac{3}{2}\right)^2\cdot2\frac{1}{3}:\frac{5}{6}=\frac{9}{4}\cdot\frac{7}{3}\cdot\frac{6}{5}=\frac{63}{10}=6\frac{3}{10}\).

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