If ${N_a} = \{ an:n \in N\} ,$ then ${N_3} \cap {N_4} = $
If $A$ and $B$ are sets, then $A \cap (B -A)$ is
If $A=\{1,2,3,4\}, B=\{3,4,5,6\}, C=\{5,6,7,8\}$ and $D=\{7,8,9,10\} ;$ find
$B \cup D$
If $X = \{ {4^n} - 3n - 1:n \in N\} $ and $Y = \{ 9(n - 1):n \in N\} ,$ then $X \cup Y$ = . . . . .
Find the union of each of the following pairs of sets :
$A=\{1,2,3\}, B=\varnothing$