Ответ:

  1. \(\frac{9}{15}=\frac{3}{5}\).
  2. \(\frac{8}{56}=\frac{1}{7}\).
  3. \(\frac{42}{90}=\frac{7}{15}\).
  4. \(\frac{38\cdot18}{9\cdot19}=\frac{2\cdot19\cdot18}{9\cdot19}=4\).

Ответ: \(\frac{3}{5};\ \frac{1}{7};\ \frac{7}{15};\ 4\).