(重发)又不明白了...三元一次方程

(12)
3x-2y=1 (1)
5x+3z=8 (2)
3y-6z=-3 (3)
(2)*2+(3)
10x+6z+3y-6z=16-3
10x+3y=13 (4)
(1)*3+(4)*2
9x-6y+20x+6y=3+26
29x=29
x=1
代入(1),3-2y=1,y=1
代入(3),3-6z=-3,z=1
所以x=1,y=1,z=1

(15)
5x-3y+4z=13 (1)
2x+7y-3z=19 (2)
3x+2y-z=18 (3)
(1)+(3)*4
5x-3y+4z+12x+8y-4z=13+72
17x+5y=85 (4)
(3)*3-(2)
9x+6y-3z-2x-7y+3z=54-19
7x-y=35 (5)
(1)+(2)*5
17x+5y+35x-5y=85+175
52x=260
x=5
代入(5),35-y=35,y=0
代入(3),15+0-z=18,z=-3
所以x=5,y=0,z=-3