Ответ:

  1. \(\frac{5a}{15b}=\frac{a}{3b}\);
  2. \(\frac{3c}{8c}=\frac{3}{8}\);
  3. \(\frac{b}{12b}=\frac{1}{12}\);
  4. \(\frac{-6}{18x}=-\frac{1}{3x}\);
  5. \(\frac{ac}{bc}=\frac{a}{b}\);
  6. \(\frac{xy}{2y}=\frac{x}{2}\).

Ответ: а) \(\frac{a}{3b}\); б) \(\frac{3}{8}\); в) \(\frac{1}{12}\); г) \(-\frac{1}{3x}\); д) \(\frac{a}{b}\); е) \(\frac{x}{2}\).