Answer:
[tex]\huge \boxed{x=21}[/tex]
Step-by-step explanation:
[tex]\Huge\textnormal{Add 12 from both sides of the equation.}[/tex]
[tex]\displaystyle x-12+12=9+12[/tex]
[tex]\Huge \textnormal{Simplify and solve to find the answer.}[/tex]
[tex]\displaystyle 9+12=21[/tex]
[tex]\huge \boxed{x=21}[/tex], which is our answer.
