X+3Y-Z=13 ①3X-2Y-Z=2 ②2X-Y+Z=-3 ③②+③,得5x-3y=-1 ④①+③,得3x+2y=10 ⑤④×2,得10x-6y=-2 ⑥⑤×3,得9x+6y=30 ⑦⑥+⑦,得19x=28,∴x=28/19把x=28/19代入④,得（140/19）-3y=-1,y=53/19把x=28/19,y=53/19代入...