5.168 Выполните сложение и вычитание: a) 4/9 + 2/9; б) 1/11 + 5/11; в) 12/19 + 7/19; г) 13/1000 + 26/1000; д) 5/7 - 2/7;\(\ne\)) 4/6 - 2/6; ж) 11/16 - 4/16; 3) 47/100 - 26/100.

Решение:

1. \( \frac{4}{9} + \frac{2}{9} = \frac{4+2}{9} = \frac{6}{9} = \frac{2}{3} \)
2. \( \frac{1}{11} + \frac{5}{11} = \frac{1+5}{11} = \frac{6}{11} \)
3. \( \frac{12}{19} + \frac{7}{19} = \frac{12+7}{19} = \frac{19}{19} = 1 \)
4. \( \frac{13}{1000} + \frac{26}{1000} = \frac{13+26}{1000} = \frac{39}{1000} \)
5. \( \frac{5}{7} - \frac{2}{7} = \frac{5-2}{7} = \frac{3}{7} \)
6. \( \frac{4}{6} - \frac{2}{6} = \frac{4-2}{6} = \frac{2}{6} = \frac{1}{3} \)
7. \( \frac{11}{16} - \frac{4}{16} = \frac{11-4}{16} = \frac{7}{16} \)
8. \( \frac{47}{100} - \frac{26}{100} = \frac{47-26}{100} = \frac{21}{100} \)

Ответ: а) \( \frac{2}{3} \); б) \( \frac{6}{11} \); в) 1; г) \( \frac{39}{1000} \); д) \( \frac{3}{7} \); е) \( \frac{1}{3} \); ж) \( \frac{7}{16} \); з) \( \frac{21}{100} \).