Ответ:

  1. \(25\frac{5}{11}+3\frac{6}{7}=28+\frac{35+66}{77}=29\frac{24}{77}\).
  2. \(14\frac{7}{9}-1\frac{1}{6}=13+\left(\frac{14}{18}-\frac{3}{18}\right)=13\frac{11}{18}\).
  3. \(2\frac{9}{20}-\left(\frac14+1\frac15\right)=2\frac{9}{20}-1\frac{9}{20}=1\).
  4. \(\frac56+\left(6\frac59-\frac14\right)=\frac56+6\frac{11}{36}=7\frac{17}{36}\).