777. Вычислите: 1) 6 4/9 + 3 5/9; 2) 10 11/19 + 5 14/19; 3) 2 3/13 + 2 11/13; 4) 1 5/8 + 3 7/8; 5) 1 − 3/11; 6) 1 − 13/40; 7) 4 − 1 4/7; 8) 10 − 9 3/10; 9) 5 2/7 − 2 5/7; 10) 14 6/20 − 8 12/20; 11) 8 3/14 − 5 9/14; 12) 7 10/21 − 4 16/21; 13) 14 8/31 − 6 8/31; 14) (12 5/22 + 7 17/22) − (13 7/23 − 9 15/23).

1. \(6\frac{4}{9}+3\frac{5}{9}=9\frac{9}{9}=10\).
2. \(10\frac{11}{19}+5\frac{14}{19}=15\frac{25}{19}=16\frac{6}{19}\).
3. \(2\frac{3}{13}+2\frac{11}{13}=4\frac{14}{13}=5\frac{1}{13}\).
4. \(1\frac{5}{8}+3\frac{7}{8}=4\frac{12}{8}=5\frac{1}{2}\).
5. \(1-\frac{3}{11}=\frac{11}{11}-\frac{3}{11}=\frac{8}{11}\).
6. \(1-\frac{13}{40}=\frac{40}{40}-\frac{13}{40}=\frac{27}{40}\).
7. \(4-1\frac{4}{7}=3-\frac{4}{7}=2\frac{3}{7}\).
8. \(10-9\frac{3}{10}=\frac{7}{10}\).
9. \(5\frac{2}{7}-2\frac{5}{7}=4\frac{9}{7}-2\frac{5}{7}=2\frac{4}{7}\).
10. \(14\frac{6}{20}-8\frac{12}{20}=6-\frac{6}{20}=5\frac{7}{10}\).
11. \(8\frac{3}{14}-5\frac{9}{14}=7\frac{17}{14}-5\frac{9}{14}=2\frac{8}{14}=2\frac{4}{7}\).
12. \(7\frac{10}{21}-4\frac{16}{21}=6\frac{31}{21}-4\frac{16}{21}=2\frac{15}{21}=2\frac{5}{7}\).
13. \(14\frac{8}{31}-6\frac{8}{31}=8\).
14. \(12\frac{5}{22}+7\frac{17}{22}=20\). Далее: \(13\frac{7}{23}-9\frac{15}{23}=3\frac{15}{23}-\frac{15}{23}=3\). Поэтому \(20-3=17\).

Ответ: 1) 10; 2) 16 6/19; 3) 5 1/13; 4) 5 1/2; 5) 8/11; 6) 27/40; 7) 2 3/7; 8) 7/10; 9) 2 4/7; 10) 5 7/10; 11) 2 4/7; 12) 2 5/7; 13) 8; 14) 17.