Answer :

mariamikayla
[tex]\frac{1}{7}(x+21)=-6 \\\\\frac{x+21}{7}=-6 \\\\ x+21=(-6)*7 \\\\ x+21=-42 \\\\ x=-42-21 \\\\ \boxed{x=-63}[/tex]
AL2006
There are several ways to do it.
Here is one way:

1/7 (x + 21) = -6

Multiply each side by  7 :            x + 21 = -42

Subtract  21  from each side :    x  =  -63