{x-y+z=0,①2x+y-2z=6,②3x-y-z=3 ③①+②,得3x-z=6 ④③-①,得2x-2z=3,即x-z=1.5 ⑤④-⑤,得2x=4.5∴x=2.25把x=2.25代入⑤,得2.25-z=1.5z=0.75把x=2.25,z=0.75代入①,得2.25-y+0.75=0y=3∴原方程组的解是：{x=2.25y...