а) 2 2/3 · (2 1/3 + 2 2/15) − 8 4/5; б) (4 5/12 + 1 3/4) : (6 2/15 − 1 1/5); в) (6 1/4 · 2 2/15 − 5 1/3 : 8/9) : 11 + 1 3/4 − 3/4

а)

\(2\frac{2}{3}=\frac{8}{3}\), \(2\frac{1}{3}=\frac{7}{3}\), \(2\frac{2}{15}=\frac{32}{15}\), \(8\frac{4}{5}=\frac{44}{5}\).

\[\frac{8}{3}\cdot\left(\frac{7}{3}+\frac{32}{15}\right)-\frac{44}{5}=\frac{8}{3}\cdot\frac{67}{15}-\frac{44}{5}=\frac{536}{45}-\frac{396}{45}=\frac{140}{45}=\frac{28}{9}.\]

б)

\(4\frac{5}{12}=\frac{53}{12}\), \(1\frac{3}{4}=\frac{7}{4}\), \(6\frac{2}{15}=\frac{92}{15}\), \(1\frac{1}{5}=\frac{6}{5}\).

\[\left(\frac{53}{12}+\frac{7}{4}\right):\left(\frac{92}{15}-\frac{6}{5}\right)=\frac{37}{6}:\frac{74}{15}=\frac{37}{6}\cdot\frac{15}{74}=\frac{5}{4}.\]

в)

\(6\frac{1}{4}=\frac{25}{4}\), \(2\frac{2}{15}=\frac{32}{15}\), \(5\frac{1}{3}=\frac{16}{3}\), \(1\frac{3}{4}=\frac{7}{4}\).

\[\left(\frac{25}{4}\cdot\frac{32}{15}-\frac{16}{3}:\frac{8}{9}\right):11+\frac{7}{4}-\frac{3}{4}=\left(\frac{40}{3}-6\right):11+1=\frac{22}{3}:11+1=\frac{2}{3}+1=\frac{5}{3}.\]

Ответ: а) \(\frac{28}{9}\); б) \(\frac{5}{4}\); в) \(\frac{5}{3}\).