记:
2x+y+z=17.①
x+2y+z=14.②
x+y+2z=13.③
①式+②式+③得4x+4y+4z=44 ,等式两边同时除以4得x+y+z=11.④
①式-④式得x=6
②式-④式得y=3
③式-④式得z=2