If $U = \{2, 3, 4, 5, 6, 7, 8, 9, 10, 11\}$,$A = \{3, 5, 7, 11\}$ and $B = \{7, 8, 9, 10, 11\}$,compute $(A - B)'$.

Domain of the function $f(x) = \frac{x - 3}{(x - 1)\sqrt{x^2 - 4}}$ is

Which of the following sets is non-empty?

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

If $A = \{a, b\}$,$B = \{2, 3, 5, 6, 7\}$ and $C = \{5, 6, 7, 8, 9\}$,find $A \times (B \cap C)$.

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