Найдите значение выражения:
а) $(\frac{7}{15} + \frac{7}{30} + \frac{4}{5}) : (2 - \frac{1}{3} - \frac{1}{2})$;
б) $17 : (\frac{3}{5} + \frac{1}{4}) + (\frac{7}{8} - \frac{1}{4}) * (\frac{4}{5})^2$.
$(\frac{7}{15} + \frac{7}{30} + \frac{4}{5}) : (2 - \frac{1}{3} - \frac{1}{2}) = (\frac{14}{30} + \frac{7}{30} + \frac{24}{30}) : (2 - \frac{2}{6} - \frac{3}{6}) = \frac{45}{30} : (2 - \frac{5}{6}) = \frac{3}{2} : 1\frac{1}{6} = \frac{3}{2} : \frac{7}{6} = \frac{3}{2} * \frac{6}{7} = \frac{3}{1} * \frac{3}{7} = \frac{9}{7} = 1\frac{2}{7}$
$17 : (\frac{3}{5} + \frac{1}{4}) + (\frac{7}{8} - \frac{1}{4}) * (\frac{4}{5})^2 = 17 : (\frac{12}{20} + \frac{5}{20}) + (\frac{7}{8} - \frac{2}{8}) * \frac{4^2}{5^2} = 17 : \frac{17}{20} + \frac{5}{8} * \frac{16}{25} = 17 * \frac{20}{17} + \frac{1}{1} * \frac{2}{5} = 20 + \frac{2}{5} = 20\frac{2}{5}$