4. Сократить дроби: a) $$\frac{7}{28}$$ б) $$\frac{24}{56}$$ в) $$\frac{42}{98}$$ г) $$\frac{60}{156}$$ д) $$\frac{300}{450}$$ e) $$\frac{6 \cdot 14}{7 \cdot 30}$$ ж) $$\frac{22 \cdot 10}{15 \cdot 33}$$ з) $$\frac{8 \cdot 7 + 8 \cdot 3}{16 \cdot 25 - 16 \cdot 5}$$

а) $$\frac{7}{28} = \frac{7:7}{28:7} = \frac{1}{4}$$ б) $$\frac{24}{56} = \frac{24:8}{56:8} = \frac{3}{7}$$ в) $$\frac{42}{98} = \frac{42:14}{98:14} = \frac{3}{7}$$ г) $$\frac{60}{156} = \frac{60:12}{156:12} = \frac{5}{13}$$ д) $$\frac{300}{450} = \frac{300:150}{450:150} = \frac{2}{3}$$ е) $$\frac{6 \cdot 14}{7 \cdot 30} = \frac{6 \cdot 2 \cdot 7}{7 \cdot 5 \cdot 6} = \frac{2}{5}$$ ж) $$\frac{22 \cdot 10}{15 \cdot 33} = \frac{2 \cdot 11 \cdot 2 \cdot 5}{3 \cdot 5 \cdot 3 \cdot 11} = \frac{2 \cdot 2}{3 \cdot 3} = \frac{4}{9}$$ з) $$\frac{8 \cdot 7 + 8 \cdot 3}{16 \cdot 25 - 16 \cdot 5} = \frac{8 \cdot (7+3)}{16 \cdot (25-5)} = \frac{8 \cdot 10}{16 \cdot 20} = \frac{80}{320} = \frac{8}{32} = \frac{1}{4}$$