А) \(7 \frac{7}{8} \cdot \frac{5}{7} = \frac{7 \cdot 8 + 7}{8} \cdot \frac{5}{7} = \frac{63}{8} \cdot \frac{5}{7} = \frac{63 \cdot 5}{8 \cdot 7} = \frac{9 \cdot 5}{8} = \frac{45}{8}\)
Ответ: \(\frac{45}{8}\)