21) \(2\frac{1}{3}\cdot1\frac{5}{9}=\)

\(2\frac{1}{3}=\frac{7}{3}\), \(1\frac{5}{9}=\frac{14}{9}\).

\[\frac{7}{3}\cdot\frac{14}{9}=\frac{98}{27}=3\frac{17}{27}.\]

Ответ: \(3\frac{17}{27}\).