Answer
$0$
Work Step by Step
Based on the graph, the $y-$value of $g$ at $x=0$ is $3$. Hence, $g(0)=3.$ The $y-$value of $f$ when $x=3$ is $0$. Hence, $f(3)=0$. The given composition function, $
(f\circ g)(0)
,$ evaluates to
\begin{array}{l}\require{cancel}
f(g(0))
\\\\=
f(3)
\\\\=
0
.\end{array}