Ответ:

а) \(2\frac{3}{4}-1\frac{5}{6}=\frac{11}{4}-\frac{11}{6}=\frac{33-22}{12}=\frac{11}{12}\).

б) \(4\frac{2}{5}+3\frac{5}{6}=7+\frac{12}{30}+\frac{25}{30}=7\frac{37}{30}=8\frac{7}{30}\).

в) \(7\frac{5}{12}-\left(1\frac{5}{8}+2\frac{1}{24}\right)=7\frac{10}{24}-\left(1\frac{15}{24}+2\frac{1}{24}\right)=7\frac{10}{24}-3\frac{16}{24}=3\frac{18}{24}=3\frac{3}{4}\).

Ответ: а) \(\frac{11}{12}\); б) \(8\frac{7}{30}\); в) \(3\frac{3}{4}\).