1)3х-21+5х=8х-21
2)10-15х+8х=-7х+10
3)(2y+10)(4-11y)=8y-22y^2+40-110y=-22y^2-102y+40
3)2y-8+10y=12y-8
4)4х+х+6=5х+6
5)6х-3х+21=3х+21