Answer
$\overline {A\cap B}=\{0,1,2,3,5,6,7,8,9\}$.
Work Step by Step
The given sets are
$A=\{1,3,4,5,9\},B=\{2,4,6,7,8\}$ and $U=\{0,1,2,3,4,5,6,7,8,9\}$
The symbol $\cap$ means the set containing common elements of the given sets.
$A\cap B=\{4\}$
The symbol $ \overline {A\cap B}$ means the set containing the elements of the union set not in set $A\cap B$.
Hence, the answer is $\overline {A\cap B}=\{0,1,2,3,5,6,7,8,9\}$.
