X/3Y=2XY/(6Y^2),
3X/(2Y^2)=9X/(6Y^2),
2. Common ground: 3a^2b^2
6c/(a^2b)= 18bc/(3a^2b^2)
c/(3ab^2)=ac/(3a^2b^2)
3. Common denominator: 2 (x+y) 2,
(x-y)/(2x+2y)=(x+y)(x-y)/[2(x+y)^2)
xy/(x+y)^2=2xy/[2(x+y)^2].
4. Common denominator: (2m+3)(2m-3),
2mn/(4m^2-9)=2mn/[(2m+3)(2m-3)]
(2m-3)/(2m+3)=(2m-3)^2/[(2m+3)(2m-3)]