1) 8x-2y-6z=23
2(4х-у-3z)=23
2(4х-у-3z)-23=0
2) 6x-4y+3z=21
2(3х-2у)+3z=21
2(3х-2у)+3z-21=0
2(3х-2у)+3(z-7)=0
3) X+2y+2z=-3
х+2(у+z)=-3
х+2(у+z)+3=0
