3X-4Y-5Z=18 ①2X+y-6z=8 ②X+3Y+Z=22 ③由③得z=22-x-3y ④④代入②得2x+y-132+6x+18y=22即8x+19y=140 ⑤④代入①得3x-4y-110+5x+15y=18即8x+11y=128 ⑥⑤-⑥得8y=12y=1.5代入⑥得12+11y=12811y=116y=116/11代入④...