[tex]f(x)=3-4x;\ g(x)=16x-3\\\\(f\circ g)(x)=(3-4x)(16x-3)=48x-9-64x^2+12x\neq12x\\\\f(x)=6x^2;\ g(x)=\dfrac{2}{x}\\\\(f\circ g)(x)=6x^2\cdot\dfrac{2}{x}=6x\cdot\dfrac{2}{1}=12x\ \ BINGO\ ;)\\\\f(x)=\sqrt{x};\ g(x)=144x\\\\(f\circ g)(x)=\sqrt{x}\cdot144x=144x\sqrt{x}\neq12x\\\\f(x)=4x;\ g(x)=3x\\\\(f\circ g)(x)=4x\cdot3x=12x^2\neq12x\\\\Answer:\boxed{f(x)=6x^2\ and\ g(x)=\frac{2}{x}}[/tex]
