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

Which of the following pairs of sets are disjoint 

$\{a, e, i, o, u\}$ and $\{c, d, e, f\}$

If $A=\{3,5,7,9,11\}, B=\{7,9,11,13\}, C=\{11,13,15\}$ and $D=\{15,17\} ;$ find

$B \cap D$

State whether each of the following statement is true or false. Justify you answer.

$\{2,6,10,14\}$ and $\{3,7,11,15\}$ are disjoint sets.

Find the union of each of the following pairs of sets :

$A = \{ x:x$ is a natural number and multiple of $3\} $

$B = \{ x:x$ is a natural number less than $6\} $

Let $A$ and $B$ be subsets of a set $X$. Then