Ответ:

  1. \(2\frac{2}{5}+3\frac{1}{5}=(2+3)+\left(\frac{2}{5}+\frac{1}{5}\right)=5\frac{3}{5}\).
  2. \(23\frac{11}{13}+7\frac{2}{13}=(23+7)+\frac{13}{13}=31\).
  3. \(4\frac{1}{4}+15=19\frac{1}{4}\).
  4. \(2\frac{2}{3}+5\frac{2}{3}=(2+5)+\frac{4}{3}=7+1\frac{1}{3}=8\frac{1}{3}\).

Ответ: а) \(5\frac{3}{5}\); б) \(31\); в) \(19\frac{1}{4}\); г) \(8\frac{1}{3}\).