y=2x-7 (1)
5x+3y+2z=2 (2)
3x-4z=4 (3)
(2)×2+(3)
13x+6y=8 (4)
(4)-(1)×6
13x+6y-6y=8-12x+42
25x=50
x=2
y=2x-7=-3
z=(3x-4)/4=1/2