x+2y=2z-x=2y+z/3=5

x=1
y=2
z=3

x=1,y=2,z=3
x+2y=5,2y+z/3=5,两式相减得x=z/3,代入2z-x=5得z=3,从而x=1,代入x+2y=5得y=2

分(1)x+2y=5
(2)2z-x=5
(3)2y+Z/3=5 用(1)+(2)=2y+2z=10(4)
用（4）-（3）=2z-z/3=5
6/3z-1/3z=5
5/3z=5
z=3