Вычислите: а) 8/13 + 3/13; б) 31/60 + 29/60; в) 18 + 4/19; г) 23 + 9/10; д) 2 7/9 + 8/9; е) 15 8/11 + 4 3/11; ж) 4 1/2 + 3 1/4; з) 5 1/7 + 3 20/21.

1. \(\frac{8}{13}+\frac{3}{13}=\frac{11}{13}\).
2. \(\frac{31}{60}+\frac{29}{60}=\frac{60}{60}=1\).
3. \(18+\frac{4}{19}=18\frac{4}{19}\).
4. \(23+\frac{9}{10}=23\frac{9}{10}\).
5. \(2\frac{7}{9}+\frac{8}{9}=2\frac{15}{9}=3\frac{2}{3}\).
6. \(15\frac{8}{11}+4\frac{3}{11}=19\frac{11}{11}=20\).
7. \(4\frac{1}{2}+3\frac{1}{4}=7+\frac{2}{4}+\frac{1}{4}=7\frac{3}{4}\).
8. \(5\frac{1}{7}+3\frac{20}{21}=8+\frac{3}{21}+\frac{20}{21}=8\frac{23}{21}=9\frac{2}{21}\).

Ответ: а) \(\frac{11}{13}\); б) \(1\); в) \(18\frac{4}{19}\); г) \(23\frac{9}{10}\); д) \(3\frac{2}{3}\); е) \(20\); ж) \(7\frac{3}{4}\); з) \(9\frac{2}{21}\).