How To Solve The System X+y+z=-1, X-y+3z=-17, 2x+y+z=-2?

X+y+z=-1 x-y+3z=-17 2x+y+z=-2  x= -1-y-z 3z-2y-z-1=-17, 2(z-y)=-16, z-y=-8, z= y-8  2(-1-y-y+8)+y+y-8=-2, 2y-2-4y+16-8=-2, -2y=-2+2-16+8, -2y=-8, y=4 z=4-8,z=-4 x=-1-4+4, x=-1 x=-1, y=4,z=-4