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

Решение:

1. \(\frac{4}{5} + \frac{4}{7} = \frac{4 \cdot 7 + 4 \cdot 5}{35} = \frac{28 + 20}{35} = \frac{48}{35}\)
2. \(\frac{3}{8} + 2\frac{11}{4} = \frac{3}{8} + \frac{8}{4} + \frac{11}{4} = \frac{3}{8} + \frac{19}{4} = \frac{3 + 19 \cdot 2}{8} = \frac{3 + 38}{8} = \frac{41}{8}\)
3. \(\frac{48}{35} \cdot \frac{41}{8} = \frac{6 \cdot 8}{35} \cdot \frac{41}{8} = \frac{6 \cdot 41}{35} = \frac{246}{35}\)

Ответ: \(\frac{246}{35}\)