3х + (х+2)=2*(3х+12)
И второе)) 25,8z-4,3*(6z+300)=25,8z

1)3х+х+2=6х+243х+х+2-6х-24=0-2х-22=0-2х=22х=-112)25,8z-25,8z-1290=25,8z25,8z-25,8z-1290-25,8z=0-1290-25,8z=0-25,8z=1290z=1290/(-25,8)=-50