11) \(2\frac{1}{3}\cdot1{,}8\)

\(2\frac{1}{3}=\frac{7}{3}\), \(1{,}8=\frac{9}{5}\).

\(\frac{7}{3}\cdot\frac{9}{5}=\frac{63}{15}=\frac{21}{5}=4\frac{1}{5}\).

Ответ: \(4\frac{1}{5}\).