365. Выполните действие: а) 1/2 + 1/3; б) 1/4 + 2/5; в) 2/3 + 1/4; г) 3/4 + 2/5; д) 5/7 − 1/6; е) 3/4 − 1/3; ж) 1/8 + 1/4; з) 2/3 − 5/9; и) 1/2 − 5/12; к) 5/12 − 2/9; л) 1/8 + 7/12; м) 3/4 − 1/6; н) 5/9 + 3/4; о) 23/40 − 3/8; п) 9/35 − 3/28.

1. \(\frac{1}{2}+\frac{1}{3}=\frac{3}{6}+\frac{2}{6}=\frac{5}{6}\).
2. \(\frac{1}{4}+\frac{2}{5}=\frac{5}{20}+\frac{8}{20}=\frac{13}{20}\).
3. \(\frac{2}{3}+\frac{1}{4}=\frac{8}{12}+\frac{3}{12}=\frac{11}{12}\).
4. \(\frac{3}{4}+\frac{2}{5}=\frac{15}{20}+\frac{8}{20}=\frac{23}{20}=1\frac{3}{20}\).
5. \(\frac{5}{7}-\frac{1}{6}=\frac{30}{42}-\frac{7}{42}=\frac{23}{42}\).
6. \(\frac{3}{4}-\frac{1}{3}=\frac{9}{12}-\frac{4}{12}=\frac{5}{12}\).
7. \(\frac{1}{8}+\frac{1}{4}=\frac{1}{8}+\frac{2}{8}=\frac{3}{8}\).
8. \(\frac{2}{3}-\frac{5}{9}=\frac{6}{9}-\frac{5}{9}=\frac{1}{9}\).
9. \(\frac{1}{2}-\frac{5}{12}=\frac{6}{12}-\frac{5}{12}=\frac{1}{12}\).
10. \(\frac{5}{12}-\frac{2}{9}=\frac{15}{36}-\frac{8}{36}=\frac{7}{36}\).
11. \(\frac{1}{8}+\frac{7}{12}=\frac{3}{24}+\frac{14}{24}=\frac{17}{24}\).
12. \(\frac{3}{4}-\frac{1}{6}=\frac{9}{12}-\frac{2}{12}=\frac{7}{12}\).
13. \(\frac{5}{9}+\frac{3}{4}=\frac{20}{36}+\frac{27}{36}=\frac{47}{36}=1\frac{11}{36}\).
14. \(\frac{23}{40}-\frac{3}{8}=\frac{23}{40}-\frac{15}{40}=\frac{8}{40}=\frac{1}{5}\).
15. \(\frac{9}{35}-\frac{3}{28}=\frac{36}{140}-\frac{15}{140}=\frac{21}{140}=\frac{3}{20}\).

Ответ: а) \(\frac{5}{6}\); б) \(\frac{13}{20}\); в) \(\frac{11}{12}\); г) \(1\frac{3}{20}\); д) \(\frac{23}{42}\); е) \(\frac{5}{12}\); ж) \(\frac{3}{8}\); з) \(\frac{1}{9}\); и) \(\frac{1}{12}\); к) \(\frac{7}{36}\); л) \(\frac{17}{24}\); м) \(\frac{7}{12}\); н) \(1\frac{11}{36}\); о) \(\frac{1}{5}\); п) \(\frac{3}{20}\).