Ответ:

  1. \(\frac{2}{3}-\frac{2}{5}=\frac{10}{15}-\frac{6}{15}=\frac{4}{15}\).
  2. \(\frac{1}{2}-\frac{1}{13}=\frac{13}{26}-\frac{2}{26}=\frac{11}{26}\).
  3. \(\frac{3}{5}-\frac{4}{7}=\frac{21}{35}-\frac{20}{35}=\frac{1}{35}\).
  4. \(\frac{5}{7}-\frac{2}{9}=\frac{45}{63}-\frac{14}{63}=\frac{31}{63}\).

Ответ: 1) \(\frac{4}{15}\); 2) \(\frac{11}{26}\); 3) \(\frac{1}{35}\); 4) \(\frac{31}{63}\).