Ответ:

  1. \(8\frac12+2\frac34=(8+2)+\left(\frac12+\frac34\right)=10+\frac54=11\frac14\).
  2. \(3\frac16-1\frac23=(3-1)+\left(\frac16-\frac23\right)=2-\frac12=1\frac12\).
  3. \(5\frac13-3\frac29=(5-3)+\left(\frac13-\frac29\right)=2+\frac19=2\frac19\).