Well, you can have lots of pairs of functions f and g.
[tex](f \circ g)(x) = f(g(x)) = 12x[/tex]
You can take
[tex]f(x) = 12x \text{ and } g(x) = x [/tex]
or
[tex]f(x) = x \text{ and } g(x) = 12x [/tex]
or
[tex]f(x) = \frac{x}{2} \text{ and } g(x) = 24x [/tex]
or ...