Answer
$\{0,1,2,3,5,6,7,8,9\}$
Work Step by Step
$\overline{A}$ = set of elements that are in the universal set, but not in $A$
$0$ is not in $A$, so it is in $\overline{A}$,
$1$ is in $A$ so it is not in $\overline{A}$,
$2$ is not in $A$, so it is in $\overline{A}$,
and so on, testing each element of $U$
$\overline{A}$ = $\{0,2,6,7,8\},\quad$
$\overline{B}$ = set of elements that are in the universal set, but not in $B$
$\overline{B}$ = $\{0,1,3,5,9\},\quad$
$\overline{A} \cup\overline{B}$ is the set of elements either in $\overline{A}$ or in $\overline{B}$ , or in both.
$\overline{A} \cup\overline{B}$ =$\{0,1,2,3,5,6,7,8,9\}$
