Solve for v -2 over 7i need to solve v and with steps

For which pairs of functions is (f•g)(x)=12x? f(x)=3-4x and g(x)=16x-3 f(x)=6x2 and g(x)= 2/x f(x)= and g(x) = 144x f(x)=4x and g(x) =3x