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

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

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

If $A, B$ and $C$ are three sets such that  $A \cap B = A \cap C$ and $A \cup B = A \cup C$ then

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?

If $A = \{ x:x$ is a natural number $\} ,B = \{ x:x$ is an even natural number $\} $ $C = \{ x:x$ is an odd natural number $\} $ and $D = \{ x:x$ is a prime number $\} ,$ find $B \cap C$

Let $A=\{2,4,6,8\}$ and $B=\{6,8,10,12\} .$ Find $A \cup B$