Ответ:

  1. \(\frac{3}{7}-\frac{13}{35}=\frac{15}{35}-\frac{13}{35}=\frac{2}{35}\).
  2. \(\frac{8}{15}+\frac{2}{25}=\frac{40}{75}+\frac{6}{75}=\frac{46}{75}\).
  3. \(\frac{1}{7}-\frac{1}{8}=\frac{8}{56}-\frac{7}{56}=\frac{1}{56}\).
  4. \(\frac{3}{8}+\frac{7}{72}=\frac{27}{72}+\frac{7}{72}=\frac{34}{72}=\frac{17}{36}\).
  5. \(\frac{13}{20}-\frac{3}{8}=\frac{26}{40}-\frac{15}{40}=\frac{11}{40}\).