Ответ:

а) \(4\frac{1}{12}\cdot1\frac{5}{7}=\frac{49}{12}\cdot\frac{12}{7}=7\).

\((7-5\frac{2}{9})\cdot\frac{3}{8}=(7-\frac{47}{9})\cdot\frac{3}{8}=\frac{16}{9}\cdot\frac{3}{8}=\frac{2}{3}\).

б) \((\frac{3}{8}+2\frac{1}{7}\cdot\frac{1}{20})\cdot1\frac{1}{3}=(\frac{3}{8}+\frac{15}{7}\cdot\frac{1}{20})\cdot\frac{4}{3}\).

\((\frac{3}{8}+\frac{3}{28})\cdot\frac{4}{3}=\frac{27}{56}\cdot\frac{4}{3}=\frac{9}{14}\).

Ответ: а) \(\frac{2}{3}\); б) \(\frac{9}{14}\).