题目打错了,最后应该是2b吧(3a+3b/5a-5b) = 3（a+b)/5(a-b) =3/5X(a+b/a-b) = 3/5x 2 = 6/5(3a-3b/2a+2b) = 3(a-b)/2(a+b ) = 3/2x(a-b/a+b) = 3/2x1/2 = 3/4所以(3a+3b/5a-5b)-(3a-3b/2a+2b) = 6/5-3/4 = 9/20 （小...