\( 3 \frac{4}{5} : \frac{9}{2} + \frac{9}{10} : 1 \frac{2}{5} - 1 \frac{1}{8} \)

Решение:

Выполним действия по порядку:

1. \( 3 \frac{4}{5} = \frac{19}{5} \)
2. \( \frac{19}{5} : \frac{9}{2} = \frac{19}{5} \cdot \frac{2}{9} = \frac{38}{45} \)
3. \( 1 \frac{2}{5} = \frac{7}{5} \)
4. \( \frac{9}{10} : \frac{7}{5} = \frac{9}{10} \cdot \frac{5}{7} = \frac{9 \cdot 1}{2 \cdot 7} = \frac{9}{14} \)
5. \( 1 \frac{1}{8} = \frac{9}{8} \)
6. \( \frac{38}{45} + \frac{9}{14} = \frac{38 \cdot 14 + 9 \cdot 45}{630} = \frac{532 + 405}{630} = \frac{937}{630} \)
7. \( \frac{937}{630} - \frac{9}{8} = \frac{937 \cdot 4 - 9 \cdot 315}{2520} = \frac{3748 - 2835}{2520} = \frac{913}{2520} \)

Ответ: \( \frac{913}{2520} \).