1) 6 − 2 7/8; 2) 5 1/3 + 2 3/15; 3) 9 5/6 − 3; 4) 7 1/4 − 3 3/5; 5) 2 8/14 + 6 18/21; 6) 10 − 4 2/5; 7) 8 1/9 − 5 5/6; 8) 1 3/10 + 3 2/5; 9) 9 1/3 − 5 2/7; 10) 4 2/3 − 1 1/6; 11) 6 2/7 + 10; 12) 7 11/16 + 2 13/24.

1. \(6-2\frac{7}{8}=5\frac{8}{8}-2\frac{7}{8}=3\frac{1}{8}\).
2. \(5\frac{1}{3}+2\frac{3}{15}=5\frac{1}{3}+2\frac{1}{5}=7+\frac{5+3}{15}=7\frac{8}{15}\).
3. \(9\frac{5}{6}-3=6\frac{5}{6}\).
4. \(7\frac{1}{4}-3\frac{3}{5}=7\frac{5}{20}-3\frac{12}{20}=3\frac{13}{20}\).
5. \(2\frac{8}{14}+6\frac{18}{21}=2\frac{4}{7}+6\frac{6}{7}=8\frac{10}{7}=9\frac{3}{7}\).
6. \(10-4\frac{2}{5}=9\frac{5}{5}-4\frac{2}{5}=5\frac{3}{5}\).
7. \(8\frac{1}{9}-5\frac{5}{6}=8\frac{2}{18}-5\frac{15}{18}=2\frac{5}{18}\).
8. \(1\frac{3}{10}+3\frac{2}{5}=1\frac{3}{10}+3\frac{4}{10}=4\frac{7}{10}\).
9. \(9\frac{1}{3}-5\frac{2}{7}=9\frac{7}{21}-5\frac{6}{21}=4\frac{1}{21}\).
10. \(4\frac{2}{3}-1\frac{1}{6}=4\frac{4}{6}-1\frac{1}{6}=3\frac{1}{2}\).
11. \(6\frac{2}{7}+10=16\frac{2}{7}\).
12. \(7\frac{11}{16}+2\frac{13}{24}=7\frac{33}{48}+2\frac{26}{48}=9\frac{59}{48}=10\frac{11}{48}\).

Ответ: 1) \(3\frac{1}{8}\); 2) \(7\frac{8}{15}\); 3) \(6\frac{5}{6}\); 4) \(3\frac{13}{20}\); 5) \(9\frac{3}{7}\); 6) \(5\frac{3}{5}\); 7) \(2\frac{5}{18}\); 8) \(4\frac{7}{10}\); 9) \(4\frac{1}{21}\); 10) \(3\frac{1}{2}\); 11) \(16\frac{2}{7}\); 12) \(10\frac{11}{48}\).