59. Найдите значение выражения: а) \(\left(\frac{11}{4}+\frac{9}{5}\right):\frac{13}{12}\); б) \(\frac{1}{\frac{1}{3}+\frac{1}{12}}\); в) \(\frac{25}{18}:\left(\frac{3}{8}-\frac{4}{9}\right)\); г) \(\left(1\frac{1}{15}+\frac{4}{7}\right)\cdot21\).

а)

\(\left(\frac{11}{4}+\frac{9}{5}\right):\frac{13}{12}=\left(\frac{55}{20}+\frac{36}{20}\right)\cdot\frac{12}{13}=\frac{91}{20}\cdot\frac{12}{13}=\frac{21}{5}=4\frac{1}{5}\).

б)

\(\frac{1}{\frac{1}{3}+\frac{1}{12}}=\frac{1}{\frac{4}{12}+\frac{1}{12}}=\frac{1}{\frac{5}{12}}=\frac{12}{5}=2\frac{2}{5}\).

в)

\(\frac{25}{18}:\left(\frac{3}{8}-\frac{4}{9}\right)=\frac{25}{18}:\left(\frac{27}{72}-\frac{32}{72}\right)=\frac{25}{18}\cdot\frac{72}{-5}=-20\).

г)

\(\left(1\frac{1}{15}+\frac{4}{7}\right)\cdot21=\left(\frac{16}{15}+\frac{4}{7}\right)\cdot21=\frac{172}{105}\cdot21=\frac{172}{5}=34\frac{2}{5}\).

Ответ: а) \(4\frac{1}{5}\); б) \(2\frac{2}{5}\); в) \(-20\); г) \(34\frac{2}{5}\).