12. Вычислите: А) 1/2 + 1/4 + 1/8 Д) 1/3 + 1/5 + 1/15 3) 2/3 + 1/2 + 1/7 Л) 4 15/49 - 2 3/14 П) 4 3/14 - 2/7 Б) 1/2 + 1/3 + 1/6 Е) 1/2 + 3/7 + 5/14 И) 3/4 + 11/12 + 4/5 M) 5 7/12 - 2 2/15 Р) 3 13/44 - 1 7/33 В) 1/3 + 1/4 + 1/2 Е) 1/3 + 5/4 + 5/7 Й) 5/12 + 3/25 + 1/7 Н) 5 2/15 - 2 7/12 С) 9 11/60 - 3 13/80 Г) 1/3 + 1/4 + 1/12 Ж) 1/4 + 1/3 + 1/5 К) 7/8 + 15/16 + 15/16 О) 4 11/14 - 2 3/7 Т) 2 3/5 - 1 6/7

12. Вычислите:

1. A) \( \frac{1}{2} + \frac{1}{4} + \frac{1}{8} = \frac{4+2+1}{8} = \frac{7}{8} \)
2. Д) \( \frac{1}{3} + \frac{1}{5} + \frac{1}{15} = \frac{5+3+1}{15} = \frac{9}{15} = \frac{3}{5} \)
3. 3) \( \frac{2}{3} + \frac{1}{2} + \frac{1}{7} = \frac{28+21+6}{42} = \frac{55}{42} = 1 \frac{13}{42} \)
4. Л) \( 4 \frac{15}{49} - 2 \frac{3}{14} = \frac{15}{49} - \frac{3}{14} = \frac{30-21}{98} = \frac{9}{98} \)
5. П) \( 4 \frac{3}{14} - \frac{2}{7} = \frac{3}{14} - \frac{4}{14} = -\frac{1}{14} \)
6. Б) \( \frac{1}{2} + \frac{1}{3} + \frac{1}{6} = \frac{3+2+1}{6} = \frac{6}{6} = 1 \)
7. Е) \( \frac{1}{2} + \frac{3}{7} + \frac{5}{14} = \frac{7+6+5}{14} = \frac{18}{14} = \frac{9}{7} = 1 \frac{2}{7} \)
8. И) \( \frac{3}{4} + \frac{11}{12} + \frac{4}{5} = \frac{45+55+48}{60} = \frac{148}{60} = \frac{37}{15} = 2 \frac{7}{15} \)
9. M) \( 5 \frac{7}{12} - 2 \frac{2}{15} = 3 \frac{7 \times 5 - 2 \times 4}{60} = 3 \frac{35-8}{60} = 3 \frac{27}{60} = 3 \frac{9}{20} \)
10. Р) \( 3 \frac{13}{44} - 1 \frac{7}{33} = 2 \frac{13}{44} - \frac{7}{33} = 2 \frac{39-28}{132} = 2 \frac{11}{132} = 2 \frac{1}{12} \)
11. В) \( \frac{1}{3} + \frac{1}{4} + \frac{1}{2} = \frac{4+3+6}{12} = \frac{13}{12} = 1 \frac{1}{12} \)
12. Е) \( \frac{1}{3} + \frac{5}{4} + \frac{5}{7} = \frac{28+105+60}{84} = \frac{193}{84} = 2 \frac{25}{84} \)
13. Й) \( \frac{5}{12} + \frac{3}{25} + \frac{1}{7} = \frac{175+36+100}{300} = \frac{311}{300} = 1 \frac{11}{300} \)
14. Н) \( 5 \frac{2}{15} - 2 \frac{7}{12} = 3 \frac{2}{15} - \frac{7}{12} = 3 \frac{8-35}{60} = 3 \frac{-27}{60} = 3 - \frac{27}{60} = 2 \frac{33}{60} = 2 \frac{11}{20} \)
15. С) \( 9 \frac{11}{60} - 3 \frac{13}{80} = 6 \frac{11}{60} - \frac{13}{80} = 6 \frac{44-39}{240} = 6 \frac{5}{240} = 6 \frac{1}{48} \)
16. Г) \( \frac{1}{3} + \frac{1}{4} + \frac{1}{12} = \frac{4+3+1}{12} = \frac{8}{12} = \frac{2}{3} \)
17. Ж) \( \frac{1}{4} + \frac{1}{3} + \frac{1}{5} = \frac{15+20+12}{60} = \frac{47}{60} \)
18. К) \( \frac{7}{8} + \frac{15}{16} + \frac{15}{16} = \frac{14+30+30}{32} = \frac{74}{32} = \frac{37}{16} = 2 \frac{5}{16} \)
19. О) \( 4 \frac{11}{14} - 2 \frac{3}{7} = 2 \frac{11}{14} - \frac{6}{14} = 2 \frac{5}{14} \)
20. Т) \( 2 \frac{3}{5} - 1 \frac{6}{7} = 1 \frac{3}{5} - \frac{6}{7} = 1 \frac{21-30}{35} = 1 - \frac{9}{35} = \frac{26}{35} \)

Ответ: А) 7/8; Д) 3/5; 3) 1 13/42; Л) 9/98; П) -1/14; Б) 1; Е) 1 2/7; И) 2 7/15; M) 3 9/20; Р) 2 1/12; В) 1 1/12; Е) 2 25/84; Й) 1 11/300; Н) 2 11/20; С) 6 1/48; Г) 2/3; Ж) 47/60; К) 2 5/16; О) 2 5/14; Т) 26/35.