tolong ya kawan itu pake cara campuran no 1 dan 2 saja

No.1
x+y-z = 0............(1)
x-y-z = 4.............(2)
x+2y+z = -4........(3)
Eliminasi x dan z dari pers (1) & (2)
x+y-z = 0
x-y-z = 4
_________-
2y = -4
y = -2
Subtitusi y ke pers (3) & (2) kemudian eliminasi x
x+2y+z = -4 => x-4+z = -4. => x+z = 0
x-y-z = 4 => x+2-z = 4 => x-z = 2
__________-
2z = -2
z = -1
Subtitusi y dan z ke pers (1)
x+y-z = 0
x-2+1 = 0
x-1 = 0
x = 1
HP{1, -2, -1}

No.2
x+3y-z = 13.........(1)
3x+y-z = 11.........(2)
x+y-3z = 11.........(3)
Eliminasi z dari pers (1) & (2)
x+3y-z = 13
3x+y-z = 11
_____________-
-2x+2y = 2.......(4)
Eliminasi z dari pers (2) & (3)
3x+y-z = 11 |×3| 9x+3y-3z = 33
x+y-3z = 11 |×1| x+y-3z = 11
________________-
8x+2y = 22.......(5)
Eliminasi y dari pers (4) & (5)
-2x+2y = 2
8x+2y = 22
____________-
-10x = -20
x = 2
Subtitusi x ke pers (2) & (3) kemudian eliminasi y
x+y-3z=11 => 2+y-3z = 11 => y-3z = 9
3x+y-z=11 => 6+y-z = 11 => y-z = 5
_____________-
-2z = 4
z = -2
Subtitusi x dan z ke pers (1)
x+3y-z = 13
2+3y+2 = 13
3y = 9
y = 3

Nilai 2x+2y-6z = 2(2)+2(3)-6(-2)
= 4+6+12
= 22