139. Найдите значение выражения: a) 1 \frac{1}{4} · 3 \frac{4}{7} : 3 \frac{4}{11}; б) (3 \frac{1}{5} + 2 \frac{1}{4})·5 - 25 \frac{5}{6}.

a) 1 \frac{1}{4} · 3 \frac{4}{7} : 3 \frac{4}{11} = \frac{5}{4} * \frac{25}{7} : \frac{37}{11} = \frac{5}{4} * \frac{25}{7} * \frac{11}{37} = \frac{5*25*11}{4*7*37} = \frac{1375}{1036} = 1 \frac{339}{1036} б) (3 \frac{1}{5} + 2 \frac{1}{4})·5 - 25 \frac{5}{6} = (\frac{16}{5} + \frac{9}{4}) * 5 - \frac{155}{6} = (\frac{64}{20} + \frac{45}{20}) * 5 - \frac{155}{6} = \frac{109}{20} * 5 - \frac{155}{6} = \frac{109}{4} - \frac{155}{6} = \frac{327}{12} - \frac{310}{12} = \frac{17}{12} = 1 \frac{5}{12}