x+y-z=11 (1)
x-3y+2z=1 (2)
3x+2y-z=4 (3)
(1)×2+(2)
3x-y=23 (4)
(2)+(3)×2
7x+y=9 (5)
(4)+(5)
10x=32
x=3.2
y=3x-23=-13.4
z=x+y-11=-21.2