4x-{2x+3[x+2(4z-x)-2y]-7y}+6z 其中x-y=-3,y-z=-1
=4x-2x-3x-6(4z-x)+6y+7y+6z
=-x-24z+6x+13y+6z
=5x+13y-18z
=5x-5y+18y-18z
=5(x-y)+18(y-z)
=5*(-3)+18*(-1)
=-33