Решим пример по действиям:
$$3\frac{9}{14} - 2\frac{4}{5} = \frac{3 \cdot 14 + 9}{14} - \frac{2 \cdot 5 + 4}{5} = \frac{42 + 9}{14} - \frac{10 + 4}{5} = \frac{51}{14} - \frac{14}{5} = \frac{51 \cdot 5 - 14 \cdot 14}{14 \cdot 5} = \frac{255 - 196}{70} = \frac{59}{70}$$
$$\frac{59}{70} : 7\frac{1}{3} = \frac{59}{70} : \frac{7 \cdot 3 + 1}{3} = \frac{59}{70} : \frac{21 + 1}{3} = \frac{59}{70} : \frac{22}{3} = \frac{59 \cdot 3}{70 \cdot 22} = \frac{177}{1540}$$
$$2\frac{13}{15} + 6\frac{5}{6} = \frac{2 \cdot 15 + 13}{15} + \frac{6 \cdot 6 + 5}{6} = \frac{30 + 13}{15} + \frac{36 + 5}{6} = \frac{43}{15} + \frac{41}{6} = \frac{43 \cdot 2 + 41 \cdot 5}{30} = \frac{86 + 205}{30} = \frac{291}{30} = \frac{97}{10} = 9\frac{7}{10}$$
$$\frac{97}{10} : 5\frac{3}{5} = \frac{97}{10} : \frac{5 \cdot 5 + 3}{5} = \frac{97}{10} : \frac{25 + 3}{5} = \frac{97}{10} : \frac{28}{5} = \frac{97 \cdot 5}{10 \cdot 28} = \frac{97}{2 \cdot 28} = \frac{97}{56} = 1\frac{41}{56}$$
Ответ: 177/1540 = 177/1540; 97/56 = 1 41/56