Solve using Gaussian Method? Please help me

-4x-9y-z=11
-8x-6y-2z=-2
6x+9y+z=-7

&

-x+y+z=-1
-x+5y-19z=-29
7x-6y-12z=0

& one more...

5x-6y+5z=13
10x-12y+10z=23
-15x+18y-15z=-37

x = 2, y = -2, z = -1

x - 6z = -6
y - 5x = -7
or
x = 6t - 6
y = 5t - 7
z = t

no solution

-4x-9y-z=11 (1)
-8x-6y-2z=-2 (2)
6x+9y+z=-7 (3)

-----

From (3),

z = - 6x - 9y - 7 (4)

sub (4) in (1)

-4x-9y-(-6x-9y-7)=11

-4x-9y+6x+9y+7=11

2x+7=11

x=2 <<<<=================

sub x = 2 in (4),

-6(2) -9y -7=z

-12-9y-7=z

z=-9y-19

sub z=-9y-19 in (2), with x=2

-8(2) -6y -2(-9y-19)=-2

-16 -6y +18y + 38 = -2
12y=-24
y=-2 <<<====================

sub y=-2 and x=2 in (4)

z=-6(2) -9(-2) -7
z=-1

therefore x = 2, y = -2, z = -1.