C) \(3 \frac{3}{5} \cdot 5 \frac{5}{8}\)

\( 3 \frac{3}{5} \cdot 5 \frac{5}{8} = \frac{3 \cdot 5 + 3}{5} \cdot \frac{5 \cdot 8 + 5}{8} = \frac{18}{5} \cdot \frac{45}{8} = \frac{18 \cdot 45}{5 \cdot 8} = \frac{18 \cdot 9 \cdot 5}{5 \cdot 8} = \frac{18 \cdot 9}{8} = \frac{9 \cdot 9}{4} = \frac{81}{4} = 20 \frac{1}{4} \)

Ответ: \(20 \frac{1}{4}\).