Solve systems of linear equations by graphing?

First, since these have 3 variables, they only graph in 3-D, not on a graph paper, so I doubt that you would WANT to use graphing to solve this. However, the solution would be where the three planes cross (assuming there is a single point where they do all intersect).

So instead, I will solve by elimination:

By adding these two equations:

x+y-z=-1

-4x+y-z=-1

we get:

-3x-2z = -2

Then, multiply 2*(-4x-y+2z)=2*(-7) to get

-8x-2y+4z=-14 and subtract

2x-2y-5z=7 from it to get

-10x+9z=-21

You can then solve this system of equations to get x and z.

-3x-2z = -2

-10x+9z=-21

Then go back to solve for y.

I hope this helps!