А. Запишите ответ в виде несократимой дроби или в виде смешанного числа с несократимой дробной частью.

Решение:

1. \( \frac{3}{8} + \frac{1}{8} = \frac{3+1}{8} = \frac{4}{8} = \frac{1}{2} \)
2. \( \frac{5}{21} + \frac{2}{21} = \frac{5+2}{21} = \frac{7}{21} = \frac{1}{3} \)
3. \( \frac{8}{15} + \frac{2}{15} = \frac{8+2}{15} = \frac{10}{15} = \frac{2}{3} \)
4. \( \frac{9}{35} + \frac{6}{35} = \frac{9+6}{35} = \frac{15}{35} = \frac{3}{7} \)
5. \( \frac{3}{22} + \frac{8}{22} = \frac{3+8}{22} = \frac{11}{22} = \frac{1}{2} \)
6. \( \frac{4}{9} + \frac{2}{9} = \frac{4+2}{9} = \frac{6}{9} = \frac{2}{3} \)
7. \( \frac{10}{21} + \frac{4}{21} = \frac{10+4}{21} = \frac{14}{21} = \frac{2}{3} \)
8. \( \frac{11}{12} - \frac{5}{12} = \frac{11-5}{12} = \frac{6}{12} = \frac{1}{2} \)
9. \( \frac{13}{15} - \frac{8}{15} = \frac{13-8}{15} = \frac{5}{15} = \frac{1}{3} \)
10. \( \frac{43}{50} - \frac{13}{50} = \frac{43-13}{50} = \frac{30}{50} = \frac{3}{5} \)
11. \( \frac{13}{24} - \frac{5}{24} = \frac{13-5}{24} = \frac{8}{24} = \frac{1}{3} \)
12. \( \frac{25}{42} - \frac{11}{42} = \frac{25-11}{42} = \frac{14}{42} = \frac{1}{3} \)
13. \( \frac{7}{15} - \frac{2}{15} = \frac{7-2}{15} = \frac{5}{15} = \frac{1}{3} \)
14. \( \frac{29}{33} - \frac{7}{33} = \frac{29-7}{33} = \frac{22}{33} = \frac{2}{3} \)
15. \( \frac{9}{10} + \frac{3}{10} = \frac{9+3}{10} = \frac{12}{10} = 1 \frac{2}{10} = 1 \frac{1}{5} \)
16. \( \frac{5}{9} + \frac{7}{9} = \frac{5+7}{9} = \frac{12}{9} = 1 \frac{3}{9} = 1 \frac{1}{3} \)
17. \( \frac{7}{15} + \frac{13}{15} = \frac{7+13}{15} = \frac{20}{15} = 1 \frac{5}{15} = 1 \frac{1}{3} \)
18. \( \frac{14}{25} + \frac{16}{25} = \frac{14+16}{25} = \frac{30}{25} = 1 \frac{5}{25} = 1 \frac{1}{5} \)
19. \( \frac{11}{14} + \frac{5}{14} = \frac{11+5}{14} = \frac{16}{14} = 1 \frac{2}{14} = 1 \frac{1}{7} \)
20. \( \frac{13}{22} + \frac{15}{22} = \frac{13+15}{22} = \frac{28}{22} = 1 \frac{6}{22} = 1 \frac{3}{11} \)
21. \( \frac{7}{12} + \frac{11}{12} = \frac{7+11}{12} = \frac{18}{12} = 1 \frac{6}{12} = 1 \frac{1}{2} \)

Ответ: 1) \( \frac{1}{2} \); 2) \( \frac{1}{3} \); 3) \( \frac{2}{3} \); 4) \( \frac{3}{7} \); 5) \( \frac{1}{2} \); 6) \( \frac{2}{3} \); 7) \( \frac{2}{3} \); 8) \( \frac{1}{2} \); 9) \( \frac{1}{3} \); 10) \( \frac{3}{5} \); 11) \( \frac{1}{3} \); 12) \( \frac{1}{3} \); 13) \( \frac{1}{3} \); 14) \( \frac{2}{3} \); 15) \( 1 \frac{1}{5} \); 16) \( 1 \frac{1}{3} \); 17) \( 1 \frac{1}{3} \); 18) \( 1 \frac{1}{5} \); 19) \( 1 \frac{1}{7} \); 20) \( 1 \frac{3}{11} \); 21) \( 1 \frac{1}{2} \).