Answer
$f\left( x \right)=\sqrt{x}\text{ and }g\left( x \right)=3-x$.
Work Step by Step
$h\left( x \right)=\sqrt{3-x}$
By observing the given function, it can be noted that the possible functions of f and g are $f\left( x \right)=\sqrt{x}\text{ and }g\left( x \right)=3-x$.
$\begin{align}
& h\left( x \right)=\left( f\circ g \right)\left( x \right) \\
& h\left( x \right)=f\left( g\left( x \right) \right) \\
\end{align}$
Use the function $g\left( x \right)=3-x$,
$h\left( x \right)=f\left( 3-x \right)$
Use the function $f\left( x \right)=\sqrt{x}$,
$h\left( x \right)=\sqrt{3-x}$
