1/a-1/b=3
(b-a)/(ab)=3
a-b=-3ab
(2a+3ab-2b)/(a-2ab-b)
=[2(a-b)+3ab]/[(a-b)-2ab]
=(-6ab+3ab)/(-3ab-2ab)
=(-6+3)/(-3-2)
=(-3)/(-5)
=3/5