269. Вычислите:

Решение:

1. \( \frac{1}{4} + \frac{3}{5} = \frac{5+12}{20} = \frac{17}{20} \)
2. \( \frac{9}{11} - \frac{2}{5} = \frac{45-22}{55} = \frac{23}{55} \)
3. \( \frac{13}{16} - \frac{9}{32} = \frac{26-9}{32} = \frac{17}{32} \)
4. \( \frac{3}{28} + \frac{5}{14} = \frac{3+10}{28} = \frac{13}{28} \)
5. \( \frac{14}{15} - \frac{7}{10} = \frac{28-21}{30} = \frac{7}{30} \)
6. \( \frac{3}{8} + \frac{1}{6} = \frac{9+4}{24} = \frac{13}{24} \)
7. \( \frac{9}{25} - \frac{7}{20} = \frac{36-35}{100} = \frac{1}{100} \)
8. \( \frac{37}{42} - \frac{17}{24} = \frac{148-119}{168} = \frac{29}{168} \)
9. \( \frac{11}{24} - \frac{3}{16} = \frac{22-9}{48} = \frac{13}{48} \)
10. \( \frac{9}{16} + \frac{7}{24} - \frac{3}{8} = \frac{27+14-18}{48} = \frac{23}{48} \)
11. \( \frac{1}{3} - \frac{1}{6} + \frac{1}{4} = \frac{4-2+3}{12} = \frac{5}{12} \)
12. \( \frac{2}{5} + \frac{4}{15} - \frac{5}{9} = \frac{18+12-25}{45} = \frac{5}{45} = \frac{1}{9} \)

Ответ: 1) \( \frac{17}{20} \); 2) \( \frac{23}{55} \); 3) \( \frac{17}{32} \); 4) \( \frac{13}{28} \); 5) \( \frac{7}{30} \); 6) \( \frac{13}{24} \); 7) \( \frac{1}{100} \); 8) \( \frac{29}{168} \); 9) \( \frac{13}{48} \); 10) \( \frac{23}{48} \); 11) \( \frac{5}{12} \); 12) \( \frac{1}{9} \).