（X+Y)/2+(X-Y)/3=6方程两边同乘以6得3(X+Y)+2(X-Y)=36化简得5x+y=364(x+y)-5(x-y)=2化简得9y-x=2解方程组5x+y=36,9y-x=2得x=7y=1
你错了！把x=7 y=1代入4(x+y)-5(x-y)=2 28-30= - 2
