Ответ:

  1. \(\frac{18}{24}=\frac{18:6}{24:6}=\frac{3}{4}\).
  2. \(\frac{28}{42}=\frac{28:14}{42:14}=\frac{2}{3}\).
  3. \(\frac{16}{20}=\frac{16:4}{20:4}=\frac{4}{5}\).
  4. \(\frac{30}{45}=\frac{30:15}{45:15}=\frac{2}{3}\).

Ответ: 1) 3/4; 2) 2/3; 3) 4/5; 4) 2/3.