8). \( (\frac{4}{5} + \frac{4}{7}) \cdot (3 \frac{3}{8} + 2 \frac{11}{4}) \)

Решение:

1. \( \frac{4}{5} + \frac{4}{7} = \frac{28}{35} + \frac{20}{35} = \frac{48}{35} \)
2. \( 3 \frac{3}{8} = \frac{27}{8} \)
3. \( 2 \frac{11}{4} = \frac{19}{4} \)
4. \( \frac{27}{8} + \frac{19}{4} = \frac{27}{8} + \frac{38}{8} = \frac{65}{8} \)
5. \( \frac{48}{35} \cdot \frac{65}{8} = \frac{6 \cdot 8}{35} \cdot \frac{65}{8} = \frac{6 \cdot 65}{35} = \frac{6 \cdot 13 \cdot 5}{7 \cdot 5} = \frac{78}{7} \)
6. \( \frac{78}{7} = 11 \frac{1}{7} \)

Ответ: \( 11 \frac{1}{7} \)