269. Вычислите: 1) 1/4 + 3/5; 2) 9/11 − 2/5; 3) 13/16 − 9/32; 4) 3/28 + 5/14; 5) 14/15 − 7/10; 6) 3/8 + 1/6.

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. \(\frac{3}{8}+\frac{1}{6}=\frac{9}{24}+\frac{4}{24}=\frac{13}{24}\).

Ответ: 1) \(\frac{17}{20}\); 2) \(\frac{23}{55}\); 3) \(\frac{17}{32}\); 4) \(\frac{13}{28}\); 5) \(\frac{7}{30}\); 6) \(\frac{13}{24}\).