(9ab^2+6abc)/3a^2b

=3ab(3b+2c)/3a^2b

=(3b+2c)/a

(9a^2+6ab+b^2)/(3a+b)

=(3a+b)^2/(3a+b)

=3a+b

(x^2-36)/(2x+ 12)

=(x+6)(x-6)/2(x+6)

=(x-6)/2

5)

x/3y=2xy/6y^2，

3x/2y^2=9x/6y^2

6)

6c/a^2b= 18c/3a^2b，

c/3ab=ac/3a^2b，

7)

x/(2x+2y)=(x+y)/2(x+y)^2，

xy/(x+y)^2=2xy/2(x+y)^2，

8)

2mn/(4m^2-9)=2mn/(2m+3)(2m-3)，

(2m-3)/(2m+3)=(2m-3)^2/(2m+3)(2m-3)