Let $\displaystyle {S}$ be the universal set, where:
$\displaystyle {S}={\left\lbrace{1},{2},{3},\ldots,{23},{24},{25}\right\rbrace}$
Let sets $\displaystyle {A}$ and $\displaystyle {B}$ be subsets of $\displaystyle {S}$, where:

Set $\displaystyle {A}={\left\lbrace{1},{6},{7},{12},{18},{20},{21},{22},{23},{24}\right\rbrace}$

Set $\displaystyle {B}={\left\lbrace{1},{6},{7},{10},{11},{14},{15},{25}\right\rbrace}$

LIST the elements in the set $\displaystyle {\left({A}\cup{B}\right)}^{{c}}$
$\displaystyle {\left[{\left({A}\cup{B}\right)}^{{c}}\right]}$= { }
Enter the elements as a list, separated by commas. If the result is the empty set, enter DNE

You may want to draw a Venn Diagram to help answer this question.