The number of non-empty subsets of the set $\{1, 2, 3, 4\}$ is

List all the elements of the following sers :

$B = \{ x:x$ is an integer $; - \frac{1}{2} < n < \frac{9}{2}\} $

Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?

$1 \in A$

Let $A=\{1,2,3,4,5,6\} .$ Insert the appropriate symbol $\in$ or $\notin$ in the blank spaces:

$ 8\, .......\, A $

Which of the following are examples of the null set

$\{ x:x$ is a natural numbers, $x\, < \,5$ and $x\, > \,7\} $

The smallest set $A$ such that $A  \cup  \{1, 2\} = \{1, 2, 3, 5, 9\}$ is