1. \(\frac{2}{5} - \frac{1}{5} = \frac{1}{5}\) <br> 3. \(\frac{2}{7} - \frac{4}{7} = -\frac{2}{7}\) <br> 5. \(\frac{3}{5} - \frac{1}{5} = \frac{2}{5}\) <br> 7. \(\frac{2}{9} - \frac{3}{9} = -\frac{1}{9}\) <br> 9. \(\frac{9}{20} - \frac{2}{20} = \frac{7}{20}\) <br> 11. \(\frac{8}{20} - \frac{3}{20} = \frac{5}{20}\) <br> 13. \(\frac{4}{15} - \frac{7}{15} = -\frac{3}{15}\) <br> 15. \(\frac{7}{11} - \frac{3}{11} = \frac{4}{11}\) <br> 17. \(\frac{9}{25} - \frac{9}{25} = 0\) <br> 19. \(\frac{5}{14} - \frac{4}{14} = \frac{1}{14}\)

Решение:

Вычитание дробей с одинаковыми знаменателями выполняется по правилу: \( \frac{a}{b} - \frac{c}{b} = \frac{a-c}{b} \). Сначала вычитаем числители, а знаменатель оставляем прежним.

1. \(\frac{2}{5} - \frac{1}{5} = \frac{2-1}{5} = \frac{1}{5}\)
2. \(\frac{2}{7} - \frac{4}{7} = \frac{2-4}{7} = \frac{-2}{7}\)
3. \(\frac{3}{5} - \frac{1}{5} = \frac{3-1}{5} = \frac{2}{5}\)
4. \(\frac{2}{9} - \frac{3}{9} = \frac{2-3}{9} = \frac{-1}{9}\)
5. \(\frac{9}{20} - \frac{2}{20} = \frac{9-2}{20} = \frac{7}{20}\)
6. \(\frac{8}{20} - \frac{3}{20} = \frac{8-3}{20} = \frac{5}{20}\)
7. \(\frac{4}{15} - \frac{7}{15} = \frac{4-7}{15} = \frac{-3}{15}\)
8. \(\frac{7}{11} - \frac{3}{11} = \frac{7-3}{11} = \frac{4}{11}\)
9. \(\frac{9}{25} - \frac{9}{25} = \frac{9-9}{25} = 0\)
10. \(\frac{5}{14} - \frac{4}{14} = \frac{5-4}{14} = \frac{1}{14}\)

Ответ:
1. \(\frac{1}{5}\)
3. \(-\frac{2}{7}\)
5. \(\frac{2}{5}\)
7. \(-\frac{1}{9}\)
9. \(\frac{7}{20}\)
11. \(\frac{5}{20}\)
13. \(-\frac{3}{15}\)
15. \(\frac{4}{11}\)
17. \(0\)
19. \(\frac{1}{14}\)