1. Combine the first and second equation, we get 2x+3z=-13
2. Combine the second and third equation, we get 3x+3z=-15
3. Multiply 2x+3z=-13 by -3 and 3x+3z=-15 by 2.
4. -6x-9z=39 and 6x+6z=-30
5. Combine them together.
-3z=9 z=-3
6. Plug-in the value back to our equation.
2x+3(-3)=-13
2x-9=-13
2x=-4
x=-2
X+y+z=-3
-2+y+-3=-3
y=2
