3x-y+z=3 ① 2x+y-3z=11 ② x+y+z=12 ③把③整理为X=12-y-z分别代入① ②并 整理得4y+2z=33⑤ y+5z=13⑥把⑥*4-⑤ 得18z=19 z=19/18把z=19/18代入⑤得4y+2*19/18=33解得y=79/9b把y=79/9和 z=19/18代入③得x+79/9+19/...