Add the last two equations to eliminate x :
(x - 2y - 3z) + (- x + y + 2z) = 0 + 3
- y - z = 3
y + z = -3
Subtract this from the first equation to eliminate z, then solve for y :
(2y + z) - (y + z) = -8 - (-3)
y = -5
Plug this into the first equation to solve for z :
2(-5) + z = -8
z = 2
Plug both of these into either the second or third equations to solve for x :
x - 2(-5) - 3(2) = 0
x = -4
