23. \(\left(1\frac{3}{4}+2\frac{4}{5}\right)\cdot30\)

\(1\frac{3}{4}=\frac{7}{4}\), \(2\frac{4}{5}=\frac{14}{5}\).

\(\left(\frac{7}{4}+\frac{14}{5}\right)\cdot30=\left(\frac{35}{20}+\frac{56}{20}\right)\cdot30=\frac{91}{20}\cdot30=\frac{273}{2}=136\frac{1}{2}\).

Ответ: \(136\frac{1}{2}\).