Question

2x + 3y - z = 0
4x + y + z = 7
-2x + y + z = 4​

Answer 1

2x + 3y - z = 0 →z=2x+3y

4x + y + z = 7

-2x + y + z = 4

{4x+y+2x+3y=7

{-2x+y+2x+3y=4

{6x+4y=7

{4y=4

$y=\frac{4}{4} \\ y=1$

$6x+4y=7 \\ 6x+4.1=7 \\ 6x=7-4 \\ 6x=3 \\ x=\frac{3}{6} \\ x=\frac{1}{2}$

$z=2.\frac{1}{2}+3.1 \\ z=1+3 \\ z=4$