Ответ:
- \(\frac{2}{7}-\frac{5}{42}=\frac{12}{42}-\frac{5}{42}=\frac{7}{42}=\frac{1}{6}\).
- \(\frac{1}{11}+\frac{1}{33}=\frac{3}{33}+\frac{1}{33}=\frac{4}{33}\).
- \(\frac{5}{12}+\frac{5}{18}=\frac{15}{36}+\frac{10}{36}=\frac{25}{36}\).
- \(\frac{4}{35}+\frac{1}{28}=\frac{16}{140}+\frac{5}{140}=\frac{21}{140}=\frac{3}{20}\).
- \(\frac{19}{20}-\frac{3}{8}-\frac{1}{5}=\frac{38}{40}-\frac{15}{40}-\frac{8}{40}=\frac{15}{40}=\frac{3}{8}\).
Ответ: 1) \(\frac{1}{6}\); 2) \(\frac{4}{33}\); 3) \(\frac{25}{36}\); 4) \(\frac{3}{20}\); 5) \(\frac{3}{8}\).
