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

$A=\{1,2,3\}, B=\varnothing$

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\} $

If ${N_a} = [an:n \in N\} ,$ then ${N_5} \cap {N_7} = $

If $A$ and $B$ are two sets, then $A \cup B = A \cap B$ iff

Let $A=\{1,2,3,4,5,6\}, B=\{2,4,6,8\} .$ Find $A-B$ and $B-A$

For any sets $\mathrm{A}$ and $\mathrm{B}$, show that

$P(A \cap B)=P(A) \cap P(B).$