Ответ:

  1. \(6:\frac{2}{7}=6\cdot\frac{7}{2}=21\).
  2. \(1:\frac{8}{19}=1\cdot\frac{19}{8}=\frac{19}{8}\).
  3. \(\frac{7}{25}:28=\frac{7}{25}\cdot\frac{1}{28}=\frac{1}{100}\).

Ответ: 1) 21; 2) \(\frac{19}{8}\); 3) \(\frac{1}{100}\).