3) 19/4 : 19/28 = 19/4 * 28/19 = 4 * 1

3) $$\frac{19}{4} : \frac{19}{28} = \frac{19}{4} \cdot \frac{28}{19} = \frac{19 \cdot 28}{4 \cdot 19} = \frac{28}{4} = 7$$

Ответ: 7