39. Вычислите: а) \(\frac{3}{7}\cdot\frac{5}{12}\cdot\frac{6}{15}\); б) \(\frac{4}{11}\cdot\frac{22}{81}\cdot\frac{9}{32}\); в) \(\frac{4}{27}\cdot\frac{3}{17}\cdot\frac{9}{20}\); г) \(\frac{11}{12}\cdot\frac{12}{13}\cdot\frac{13}{14}\).

\[\frac{3}{7}\cdot\frac{5}{12}\cdot\frac{6}{15}=\frac{3\cdot5\cdot6}{7\cdot12\cdot15}=\frac{3}{84}=\frac{1}{28}.\]

Ответ: \(\frac{1}{28}\).

\[\frac{4}{11}\cdot\frac{22}{81}\cdot\frac{9}{32}=\frac{4\cdot22\cdot9}{11\cdot81\cdot32}=\frac{1}{36}.\]

Ответ: \(\frac{1}{36}\).

\[\frac{4}{27}\cdot\frac{3}{17}\cdot\frac{9}{20}=\frac{4\cdot3\cdot9}{27\cdot17\cdot20}=\frac{1}{255}.\]

Ответ: \(\frac{1}{255}\).

\[\frac{11}{12}\cdot\frac{12}{13}\cdot\frac{13}{14}=\frac{11}{14}.\]

Ответ: \(\frac{11}{14}\).