(7 3/4 + 2 4/5) · 30 =

\(7\frac{3}{4}=\frac{31}{4}\), \(2\frac{4}{5}=\frac{14}{5}\).

\(\left(\frac{31}{4}+\frac{14}{5}\right)\cdot30=\left(\frac{155}{20}+\frac{56}{20}\right)\cdot30=\frac{211}{20}\cdot30=\frac{633}{2}=316\frac{1}{2}\).

Ответ: \(316\frac{1}{2}\).