解：7x+2y-z=7,............(1)6x-y+z=7,................(2)4x+3y+z=9..........(3)(1)+(2):13x+y=14y=14-13x...........(4)(3)-(2):-2x+4y=2x=2y-1...........(5)将(5)代入（4）：y=14-13x=14-13(2y-1)=27-26yy=1x=1z=2
