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
$B \cap D$
$A = \{ x:x$ is a natural number $\} = \{ 1,2,3,4,5 \ldots \} $
$B = \{ x:x$ is an even natural number $\} = \{ 2,4,6,8 \ldots \} $
$C = \{ x:x$ is an odd natural number $\} = \{ 1,3,5,7,9 \ldots \} $
$D = \{ x:x$ is a primenumber $\} = \{ 2,3,5,7 \ldots \}$
$B \cap D=\{2\}$
If $A=\{3,6,9,12,15,18,21\}, B=\{4,8,12,16,20\},$ $C=\{2,4,6,8,10,12,14,16\}, D=\{5,10,15,20\} ;$ find
$C-B$
If $X$ and $Y$ are two sets such that $X \cup Y$ has $18$ elements, $X$ has $8$ elements and $Y$ has $15$ elements ; how many elements does $X \cap Y$ have?
If $A$ and $B$ are disjoint, then $n(A \cup B)$ is equal to
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