In general [tex]\left( f\circ g \right)(x) = f\left(g(x)\right)[/tex], so in your case you need to work out [tex]\left( f\circ g \right)(5) = f\left(g(5)\right)[/tex].
You start by finding [tex]g(5) = (5)^2 - 2(5) -3[/tex].
Once you work that out, you'll then plug that answer in as an x-value into [tex]f(x)[/tex].
That will give you your final answer.
