(1) x+2y-3z=12
x-3y+2z=-13
x-y-z=0
2y-2z=10 -2y+3z=-13
z=-3 y=2 x=-1
(2) x+ y-z =0
5x-y+z=18
2x+5y+3z= -1
6x=18
x=3
y-z=-3 3y-3z=-9
5y+3z=-7
y=-2 z=1 x=3