3) (7/15 + 7/30 + 4/5) : (2 − 1/3 − 1/2)

Решение:

\( (\frac{7}{15} + \frac{7}{30} + \frac{4}{5}) : (2 - \frac{1}{3} - \frac{1}{2}) \)

1. \( \frac{7}{15} + \frac{7}{30} + \frac{4}{5} = \frac{14}{30} + \frac{7}{30} + \frac{24}{30} = \frac{45}{30} = \frac{3}{2} \)
2. \( 2 - \frac{1}{3} - \frac{1}{2} = \frac{12}{6} - \frac{2}{6} - \frac{3}{6} = \frac{7}{6} \)
3. \( \frac{3}{2} : \frac{7}{6} = \frac{3}{2} \cdot \frac{6}{7} = \frac{18}{14} = \frac{9}{7} \)

Ответ: \( \frac{9}{7} \)