269. Вычислите: 1) \(\frac{1}{4}+\frac{3}{5}\); 2) \(\frac{9}{11}-\frac{2}{5}\); 3) \(\frac{13}{16}-\frac{9}{32}\); 4) \(\frac{3}{28}+\frac{5}{14}\); 5) \(\frac{14}{15}-\frac{7}{10}\); 6) \(\frac{3}{8}+\frac{1}{6}\); 7) \(\frac{9}{25}-\frac{7}{20}\); 8) \(\frac{37}{42}-\frac{17}{24}\); 9) \(\frac{11}{24}-\frac{3}{16}\); 10) \(\frac{9}{16}+\frac{7}{24}-\frac{3}{8}\); 11) \(\frac{1}{3}-\frac{1}{6}+\frac{1}{4}\); 12) \(\frac{2}{5}+\frac{4}{15}-\frac{5}{9}\).

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

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) \(\frac{1}{9}\).