x+3y=y-2z=x+z=5
x+3y=x+z,得z=3y
代入z,y-2z=5,得 y-6y=5,即 -5y=5,y=-1
x+3y=5,得 x=5-3y=5-3*(-1)=8
x+z=5,得z=5-x=5-8=-3
因此 x=8 y=-1 z=-3