а) \( \frac{3a+12b}{6ab} = \frac{3(a+4b)}{6ab} = \frac{a+4b}{2ab} \)
б) \( \frac{15b-20c}{10b} = \frac{5(3b-4c)}{10b} = \frac{3b-4c}{2b} \)
в) \( \frac{2a-4}{3(a-2)} = \frac{2(a-2)}{3(a-2)} = \frac{2}{3} \)
г) \( \frac{5x(y+2)}{6y+12} = \frac{5x(y+2)}{6(y+2)} = \frac{5x}{6} \)
д) \( \frac{a-3b}{a^2-3ab} = \frac{a-3b}{a(a-3b)} = \frac{1}{a} \)
е) \( \frac{3x^2+15xy}{x+5y} = \frac{3x(x+5y)}{x+5y} = 3x \)
Ответ: а) \( \frac{a+4b}{2ab} \); б) \( \frac{3b-4c}{2b} \); в) \( \frac{2}{3} \); г) \( \frac{5x}{6} \); д) \( \frac{1}{a} \); е) \( 3x \).