Let $\mathrm{X}=\{\mathrm{n} \in \mathrm{N}: 1 \leq \mathrm{n} \leq 50\} .$ If $A=\{n \in X: n \text { is a multiple of } 2\}$ and $\mathrm{B}=\{\mathrm{n} \in \mathrm{X}: \mathrm{n} \text { is a multiple of } 7\},$ then the number of elements in the smallest subset of $X$ containing both $\mathrm{A}$ and $\mathrm{B}$ is

If $A, B, C$ are three sets, then $A \cap (B \cup C)$ is equal to

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

$X =\{1,3,5\} \quad Y =\{1,2,3\}$

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

$A-D$

If $X = \{ {4^n} - 3n - 1:n \in N\} $ and $Y = \{ 9(n - 1):n \in N\} ,$ then $X \cup Y$ = . . . . .

Which of the following pairs of sets are disjoint 

$\{1,2,3,4\}$ and $\{ x:x$ is a natural number and $4\, \le \,x\, \le \,6\} $