Let $U=\{1, 2, 3, 4, 5, 6, 7, 8, 9\}$,$A=\{1, 2, 3, 4\}$,$B=\{2, 4, 6, 8\}$,and $C=\{3, 4, 5, 6\}$. Find $(A \cup B)'$.

For each positive real number $\lambda$,let $A_\lambda$ be the set of all natural numbers $n$ such that $|\sin(\sqrt{n+1}) - \sin(\sqrt{n})| < \lambda$. Let $A_\lambda^c$ be the complement of $A_\lambda$ in the set of all natural numbers. Then,

If $A$ and $B$ are two given sets,then $A \cap (A \cap B)^c$ is equal to

Let $U$ be the universal set of all the students of Class $XI$ of a coeducational school and $A$ be the set of all girls in Class $XI$. Find $A'$.

Taking the set of natural numbers as the universal set,write down the complement of the following set:
$A = \{ x : x \text{ is an odd natural number} \}$

Given $n(U) = 20$,$n(A) = 12$,$n(B) = 9$,$n(A \cap B) = 4$,where $U$ is the universal set,$A$ and $B$ are subsets of $U$,then $n((A \cup B)^C) = $