If 4x−y+2z=7,6x+3y+3z=5, compute y.
Multiply FIRST equation by - 1.5 to get
-6x +1.5y -3z = -10.5 add it to second equation
6x +3y +3z =5
to get
4.5y = -5.5
y = -1.222 ( or - 11/9)