x+y+z=6 (1)
x-z=2 (2)
2x-y+z=5 (3)
(1)+(3)
3x+2z=11 (4)
(2)×2+(2)
2x+3x=4+11
5x=15
所以
x=3
z=x-2=1
y=6-x-z=2