[tex](fog)(x)=f(g(x))\\\\f(g(x))=3(2x+ak)+4\\\\f(g(x))=6x+3ak+4\\\\\boxed{f(g(x))=6x+(3ak+4)}[/tex]
E,
[tex](gof)(x)=g(f(x))\\\\g(f(x))=2(3x+4)+ak\\\\g(f(x))=6x+8+ak\\\\\boxed{g(f(x))=6x+(ak+8)}[/tex]
Igualando-as,...
[tex]f(g(x))=g(f(x))\\\\6x+(3ak+4)=6x+(ak+8)\\\\6x+3ak+4=6x+ak+8\\\\3ak-ak=6x+8-6x-4\\\\2ak=4\\\\k=\frac{4}{2a}\\\\\boxed{\boxed{k=\frac{2}{a}}}[/tex]
