Write the following sets in roster form :

$C = \{ x:x{\rm{ }}$ is a two-digit natural number such that sum of its digits is $8\} $

$C = \{ x:x{\rm{ }}$ is a two-digit natural number such that the sumof its digits is $8\} $

The elements of this set are $17,26,35,44,53,62,71$ and $80$ only.

Therefore, this set can be written in roster form as $C=\{17,26,35,44,53,62,71,80\}$

How many elements has $P(A),$ if $A=\varnothing ?$

Write the set $A = \{ 1,4,9,16,25, \ldots .\} $ in set-builder form.

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

$\{1,2,3\}\subset A$

Make correct statements by filling in the symbols $\subset$ or $ \not\subset $ in the blank spaces:

$\{a, b, c\} \ldots\{b, c, d\}$

Examine whether the following statements are true or false :

$\{ a,e\} \subset \{ x:x$ is a vowelin the English alphabet $\} $