State which of the following sets are finite or infinite :
$\{ x:x \in N$ and $x$ is odd $\} $
Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?
$\{\varnothing\} \subset A$
Write the following sets in the set-builder form :
$\{ 3,6,9,12\}$
Let $A=\{1,2,3,4,5,6\} .$ Insert the appropriate symbol $\in$ or $\notin$ in the blank spaces:
$ 8\, .......\, A $
The number of proper subsets of the set $\{1, 2, 3\}$ is