Question

I need help can someone please show me how to do this? I know how to do them but this one is different and I want to know Im doing it right.
Use the substitution method to solve the following system of equations.

x + 2y – z = 7
4x – y + 3z = –2
2x + 2y – z = 9

Answer 1

i know how to do it when itonly has x and y but this one added z and im not sure what steps to take in solving it cause the substitution process is getting a variable by itself and the rest of the problem is on the other side of the equal sign and then you plug that in to whatever variable you solved for in the second problem. so I know how to do it but i dont know how to do it with an extra variable if that makes sense.

Answer 2

it is also a multiple choice quesstion: but I dont want to guess I want to know how to do it.
(2, 1, 3)

(2, 1, –3)

(–2, 1, –3)

(–2, –1, 3)