(2X-Y)-2(3X-1/2Y)
=2x-y-6x+y
=8x
6(X/3+X-1/2)
=2x+6x-3
=8x-3
(X-3)-(5X+7)
=x-3-5x-7
=-4x-10
-4X-(-(3/1X)+(-1/4X) 题目有问题