Answer
$f(g(x))=f(\frac{x}{2}-3)=2(\frac{x}{2}-3)+6=x-6+6=x$
$g(f(x))=g(2x+6)=\frac{2x+6}{2}-3=x+3-3=x$
There are no values to be excluded.
Work Step by Step
$f(g(x))=f(\frac{x}{2}-3)=2(\frac{x}{2}-3)+6=x-6+6=x$
$g(f(x))=g(2x+6)=\frac{2x+6}{2}-3=x+3-3=x$
There are no values to be excluded.