Ответ:

  1. \(\frac{3}{12}=\frac{3\div3}{12\div3}=\frac{1}{4}\).
  2. \(\frac{18}{54}=\frac{18\div18}{54\div18}=\frac{1}{3}\).
  3. \(\frac{11}{88}=\frac{11\div11}{88\div11}=\frac{1}{8}\).

Ответ: \(\frac{1}{4};\ \frac{1}{3};\ \frac{1}{8}\).