1.x-y=5
x+z=-7
y-z=-8
2.3x+2y+5z=2
x-2y-z=6
4x+2y-7z=30
3.2x+y=3
3x-y+z=8
x+2y+3z=3
4.x+y=13
y+z=11
z+x=12
5.5x-3y+z=2
5x+2y-4z=3
-5x+y-z=2
6.x+y=-2
x+z=13
y+z=1
7.x-y-z=-1
3x+5y+7z=11
4x-y+2z=-1
8.2x+3y-z=11
2x+y=7z
2y-3z=0
求xyz.快.