Answer
$(-1, 2, -2)$
Work Step by Step
Re-arrange the given two equations to get
$4x-2y+4z=-16 $ and $6x-2y-8z =6$
$5x+z=-7 \implies 55x+11z =-77$ ....(1)
and $7x-11z=15$ ...(2)
$(55x+11z)+(7x-11z)=-77+15$
This gives: $x=-1$
Now, $5(-1)+z=-7 \implies z=-2$
and $2(-1)-y+2(-2)=-8 $ gives: $y=2$
Our solution is: $(-1, 2, -2)$
