Solve the system x - y + z = 0 (1) x + y + z = -2 (2) x + y - z = 8 (3) This system is special. It is possible to solve it using the mental math only. Distract first equation from the second ((1) from (2)). You will get 2y = -2. Hence, y = -1. Next, distract equation (3) from (2). You will get 2z = -10. Hence, z = -5. Finally, substitute the found values y= -1 and z= -5 into the first equation. You will get x - (-1) + (-5) = 0, or x = 5 - 1 = 4. Answer. The solution is x= 4, y= -1 and z= -5.