Step-by-step explanation:
several possibilities to solve this.
let's start with subtracting the second equation from the first
-x + 2y - z = 0
- -x - y +2z = 0
-------------------------
0 3y - 3z = 0
y - z = 0
y = z
now we use this in e.g. the first equation :
-x + 2z - z = 0
-x + z = 0
z = x (therefore, also x = y)
now we use this in the third equation :
2x - x = 8
x = 8 = y = z
