Ответ:

  1. \(\frac{11}{12}\cdot\frac{24}{55}=\frac{2}{5}\).
  2. \(\frac{7}{15}\cdot\frac{51}{28}\cdot\frac{60}{17}=\frac{3}{2}\).
  3. \(9\cdot\frac{13}{18}=\frac{13}{2}=6\frac{1}{2}\).
  4. \(1\frac{1}{4}\cdot2\frac{2}{15}=\frac{5}{4}\cdot\frac{32}{15}=\frac{8}{3}=2\frac{2}{3}\).

Ответ: а) \(\frac{2}{5}\); б) \(1\frac{1}{2}\); в) \(6\frac{1}{2}\); г) \(2\frac{2}{3}\).