Ответ:

  1. а) \(\frac{1}{2}+\frac{1}{3}=\frac{3}{6}+\frac{2}{6}=\frac{5}{6}\).
  2. б) \(\frac{1}{3}+\frac{2}{7}=\frac{7}{21}+\frac{6}{21}=\frac{13}{21}\).
  3. в) \(\frac{3}{7}+\frac{4}{9}=\frac{27}{63}+\frac{28}{63}=\frac{55}{63}\).
  4. г) \(\frac{1}{6}+\frac{1}{3}=\frac{1}{6}+\frac{2}{6}=\frac{1}{2}\).
  5. д) \(\frac{5}{9}-\frac{1}{6}=\frac{10}{18}-\frac{3}{18}=\frac{7}{18}\).
  6. е) \(\frac{9}{5}-\frac{7}{10}=\frac{18}{10}-\frac{7}{10}=\frac{11}{10}=1\frac{1}{10}\).
  7. ж) \(\frac{1}{6}+\frac{1}{3}=\frac{1}{2}\).
  8. з) \(\frac{3}{8}+\frac{5}{12}=\frac{9}{24}+\frac{10}{24}=\frac{19}{24}\).
  9. и) \(\frac{7}{15}-\frac{3}{10}=\frac{14}{30}-\frac{9}{30}=\frac{1}{6}\).
  10. к) \(\frac{5}{11}+\frac{3}{5}=\frac{25}{55}+\frac{33}{55}=\frac{58}{55}=1\frac{3}{55}\).
  11. л) \(\frac{3}{8}+\frac{5}{12}=\frac{19}{24}\).
  12. о) \(\frac{17}{30}-\frac{3}{6}=\frac{17}{30}-\frac{15}{30}=\frac{1}{15}\).

Ответ: а) \(\frac{5}{6}\); б) \(\frac{13}{21}\); в) \(\frac{55}{63}\); г) \(\frac{1}{2}\); д) \(\frac{7}{18}\); е) \(1\frac{1}{10}\); ж) \(\frac{1}{2}\); з) \(\frac{19}{24}\); и) \(\frac{1}{6}\); к) \(1\frac{3}{55}\); л) \(\frac{19}{24}\); о) \(\frac{1}{15}\).