x+y+z=3 (1)
3x+2y-z=5 (2)
x-3y+2z=5 (3)
(1)+(2)
4x+3y=8 (4)
(2)×2+(2)
7x+y=15 (5)
(5)×3-(4)
21x-4x=45-8
17x=37
所以
x=37/17
y=15-7x=-4/17
z=3-x-y=18/17