Giúp e với a Helppppppppppppppppppppp

`a,(-3)*x+12=21`

`=>-3x=21-12`

`=>-3x=9`

`=>x=9:(-3)`

`=>x=-3`

Vậy `x=-3`

$\\$

`b,5*(x+7)=15`

`=>5x+35=15`

`=>5x=15-35`

`=>5x=-20`

`=>x=-20:5`

`=>x=-4`

Vậy `x=-4`

$\\$

`c,2*x+7*2=(-8)*3`

`=>2x+14=-24`

`=>2x=-24-14`

`=>2x=-38`

`=>x=-38:2`

`=>x=-19`

Vậy `x=-19`

$\\$

`d,37-2*(x+6)=29`

`=>2x+12=37-29`

`=>2x+12=8`

`=>2x=8-12`

`=>2x=-4`

`=>x=-4:2`

`=>x=-2`

Vậy `x=-2`