How do I solve without the other 2 variables

Question

2x-5y-z=3

-2y=6

y=-3x-4z+1

 

What do I do when the middle equation does not have an "x" or "z"

Answer 1

The middle equation allows you to solve for y

-2y=6

so

2y=-6

y=-3

if -3=y then the top formula is

2x-5(-3)-z=3

2x+15-z=3

2x-z=-12

the bottom formula becomes

-3=-3x-4z+1

-4=-3x-4z

you now have 2 equations with 2 unknowns