If ${N_a} = \{ an:n \in N\} ,$ then ${N_3} \cap {N_4} = $

If $n(A) = 3$, $n(B) = 6$ and $A \subseteq B$. Then the number of elements in $A \cup B$ is equal to

If $X$ and $Y$ are two sets such that $X \cup Y$ has $50$ elements, $X$ has $28$ elements and $Y$ has $32$ elements, how many elements does $X$ $\cap$ $Y$ have?

$A$ and $B$ are two subsets of set $S$ = $\{1,2,3,4\}$ such that $A\ \cup \ B$ = $S$ , then number of ordered pair of $(A, B)$ is 

If $X$ and $Y$ are two sets such that $X$ has $40$ elements, $X \cup Y$ has $60$ elements and $X$ $\cap\, Y$ has $10$ elements, how many elements does $Y$ have?

If $A=\{x \in R:|x|<2\}$ and $B=\{x \in R:|x-2| \geq 3\}$ then