3) \(1\frac{3}{5}\cdot3\frac{3}{4}\)

\(1\frac{3}{5}=\frac{8}{5}\), \(3\frac{3}{4}=\frac{15}{4}\).

\(\frac{8}{5}\cdot\frac{15}{4}=6\).

Ответ: \(6\)