x+2y+3z=15 (1)
3x-6y-z=5 (2)
2x-4y+3z=18 (3)
(1)+(2)×3
7x-10y=69 (4)
(3)-(1)
x-6y=3 (5)
(4)-(5)×7
32y=48
所以
y=3/2
x=6y+3=12
z=3x-6y-5=22