Ответ:

а)

\(12\frac{1}{3}-11\frac{1}{4}=\frac{37}{3}-\frac{45}{4}=\frac{148-135}{12}=\frac{13}{12}\).

\(14-9\frac{8}{15}=\frac{210}{15}-\frac{143}{15}=\frac{67}{15}\).

\(\frac{13}{12}+\frac{67}{15}=\frac{65}{60}+\frac{268}{60}=\frac{333}{60}=5\frac{11}{20}\).

в)

\(14\frac{2}{3}-5\frac{5}{9}=\frac{44}{3}-\frac{50}{9}=\frac{82}{9}\).

\(3\frac{7}{8}+4\frac{5}{6}=\frac{31}{8}+\frac{29}{6}=\frac{209}{24}\).

\(10\frac{3}{4}-4\frac{4}{9}=\frac{43}{4}-\frac{40}{9}=\frac{227}{36}\).

\(\frac{82}{9}-\frac{209}{24}+\frac{227}{36}=\frac{656}{72}-\frac{627}{72}+\frac{454}{72}=\frac{483}{72}=\frac{161}{24}=6\frac{17}{24}\).

Ответ: а) \(5\frac{11}{20}\); в) \(6\frac{17}{24}\).