You start with
[tex](f\circ g) (-3) = f(g(-3))[/tex]
You first find
[tex]g(-3) = -3-2 = -5[/tex]
You then substitute that back into the first line
[tex]f(g(-3)) = f(-5) = 5(-5)^2-4 = 125-4 = 121[/tex]
So, [tex](f\circ g) (-3) = 121[/tex]
