## Precalculus (6th Edition) Blitzer

$(-1, 2, -2)$
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: $(-1, 2, -2)$