Question 83015
your setup looks OK


D=-12+27-1-9-12-3=-10 ... Dx=-36+162-14-54-36-42=-20 ... Dy=56+108-18-(-42)-216-12=-40
Dz=-216+126+12+108-56-54=-80


so, by Cramer, x=2, y=4, and z=8