x/2+y+(x-y)/3 = 6..........................A2(x+y)-12 = -4...............................B由B可知，x+y=4，即 y= 4-x,代入A中可得 x/2+4-x+(2x-4)/3 = 6整理式子得，(左右同乘6)3x+24-6x+4x-8 = 36x = 20所以，y = -16
