Ответ:

  1. \(\frac{14}{21}=\frac{14:7}{21:7}=\frac{2}{3}\).
  2. \(\frac{6}{9}=\frac{6:3}{9:3}=\frac{2}{3}\).
  3. \(\frac{88}{99}=\frac{88:11}{99:11}=\frac{8}{9}\).

Ответ: а) \(\frac{2}{3}\); б) \(\frac{2}{3}\); в) \(\frac{8}{9}\).