-2x+y+4z = 5 (1)
x+3y-z = 2 (2)
4x+y-6z = 11 (3)
Multiplly (2) by - 4 and add it to (3)
-4x - 12y + 4z = - 8
4x + y - 6z = 11
--------------------------
-11y - 2z = 3 (4)
Multiply (2) by 2 and add it to (1)
2x + 6y - 2z = 4
-2x + y + 4z = 5
----------------------
7y + 2z = 9 (5)
Add (4) and (5)
-11y - 2z = 3
7y + 2z = 9
-----------------
-4y = 12 divide both sides by -4
y = -3
And using (5) .... 7(-3) + 2z = 9 → -21 + 2z = 9 → 2z = 30 → z = 15
And using (2) ...... x+3(-3) - 15 = 2 → x - 9 - 15 = 2 → x = 26
So { x, y, z } = { 26, -3, 15 }