ANSWER
[tex]g(f(x)) = 2x - 6.[/tex]
EXPLANATION
The given functions are;
[tex]f(x) = 3 - x[/tex]
and
[tex]g(x) = - 2x[/tex]
We now find
[tex]g(f(x)) = g(3 - x)[/tex]
We plug in f(x) into g(x) to get,
[tex]g(f(x)) = - 2(3 - x)[/tex]
We expand parenthesis to get,
[tex]g(f(x)) = - 6 + 2x[/tex]
Or
[tex]g(f(x)) = 2x - 6[/tex]