｛2x-y-z=3
问题描述：
｛2x-y-z=3
｛4x+2y-z=15
｛4x+3y=18
答
2x-y-z=3 (1)
4x+2y-z=15 (2)
4x+3y=18 (3)
(2)-(1)
2x+3y=12 (4)
(3)-(4)
2x=6
x=3
y=(18-4x)/3=2
z=2x-y-3=1