Ответ:

  1. а) \(\frac{5}{12}-\frac{1}{3}=\frac{5}{12}-\frac{4}{12}=\frac{1}{12}\). Проверка: \(\frac{1}{12}+\frac{4}{12}=\frac{5}{12}\).
  2. б) \(\frac{1}{5}-\frac{3}{20}=\frac{4}{20}-\frac{3}{20}=\frac{1}{20}\). Проверка: \(\frac{1}{20}+\frac{3}{20}=\frac{4}{20}=\frac{1}{5}\).
  3. в) \(\frac{7}{8}-\frac{5}{12}=\frac{21}{24}-\frac{10}{24}=\frac{11}{24}\). Проверка: \(\frac{11}{24}+\frac{10}{24}=\frac{21}{24}=\frac{7}{8}\).
  4. г) \(\frac{9}{10}-\frac{1}{6}=\frac{27}{30}-\frac{5}{30}=\frac{22}{30}=\frac{11}{15}\). Проверка: \(\frac{11}{15}+\frac{1}{6}=\frac{22}{30}+\frac{5}{30}=\frac{27}{30}=\frac{9}{10}\).

Ответ: а) \(\frac{1}{12}\); б) \(\frac{1}{20}\); в) \(\frac{11}{24}\); г) \(\frac{11}{15}\).