If F(x) = 3x and g(x) = 2x, what is (g.f) (x)?

Composition of functions:
[tex](f\circ g)(x)=f(g(x))[/tex]Substitute the x in f for g(x):
[tex](f\circ g)(x)=3(g(x))=3(2x)=6x[/tex]