Ответ:

  1. а) \(\frac{3}{14}+\frac{1}{28}=\frac{6}{28}+\frac{1}{28}=\frac{7}{28}=\frac{1}{4}\).
  2. б) \(\frac{4}{15}-\frac{3}{25}=\frac{20}{75}-\frac{9}{75}=\frac{11}{75}\).
  3. в) \(\frac{5}{46}+\frac{4}{69}=\frac{15}{138}+\frac{8}{138}=\frac{23}{138}=\frac{1}{6}\).

Ответ: а) \(\frac{1}{4}\); б) \(\frac{11}{75}\); в) \(\frac{1}{6}\).