Answer
$\begin{align}
\textbf{(a)}&(f\bullet g)(3)=49\\&(g\bullet f)(3)=19
\end{align}$
$\begin{align}
\textbf{(b)}&(f\bullet g)(x)=4x^2+4x+1\\&(g\bullet f)(x)=2x^2+1
\end{align}$
Work Step by Step
$f(x)=x^2$ and $g(x)=2x+1$
(a) $(f\bullet g)(3)$ and $(g\bullet f)(3)$
$\begin{align}
(f\bullet g)(3)&=f(g(3))\\&=f(2(3)+1)\\&=f(7)\\&=7^2=49
\end{align}$
$\begin{align}
(g\bullet f)(3)&=g(f(3))\\&=g(3^2)\\&=g(9)\\&=2(9)+1\\&=18+1=19
\end{align}$
(b) $(f\bullet g)(x)$ and $(g\bullet f)(x)$
$\begin{align}
(f\bullet g)(x)&=f(g(x))\\&=f(2x+1)\\&=(2x+1)^2\\&=4x^2+4x+1
\end{align}$
$\begin{align}
(g\bullet f)(x)&=g(f(x))\\&=g(x^2)\\&=2x^2+1
\end{align}$
