19) \(4\frac{1}{4}\cdot1\frac{40}{51}=\)

\(4\frac{1}{4}=\frac{17}{4}\), \(1\frac{40}{51}=\frac{91}{51}\).

\[\frac{17}{4}\cdot\frac{91}{51}=\frac{1}{4}\cdot\frac{91}{3}=\frac{91}{12}=7\frac{7}{12}.\]

Ответ: \(7\frac{7}{12}\).