3x-2y+z=6 (1)
x+3y-z=4 (2)
7x-5y+3z=-2 (3)
(1)+(2)
4x+y=10 (4)
(2)×3+(3)
10x+4y=10
5x+2y=5 (5)
(4)×2-(5)
8x-5x=20-5
3x=15
所以
x=5
y=10-4x=-10
z=x+3y-4=-29