Solving by elimination or subsitution.

Hey guys it has been so long since I have done a lot of algebra and I am working on this take home assignment and am trying hard to figure out how to tackle some of these.

The instructions state: "Solve the following systems of equations by elimination, substitution, or graphically.

A:) 3x-y=6 & x+4y=3 B:) y+2=-x^2+1 & x2+1=2y+6 C:) x-2y+3z=10 & 2x-3y-z=8 & 5x-9y+8z=20

For A I got X being 2 1/3 and Y being 3. I am struggling on the other two. Any help is appreciated.