Which of the following are sets ? Justify your answer.

The collection of all even integers.

Set $A$ has $m$ elements and Set $B$ has $n$ elements. If the total number of subsets of $A$ is $112$ more than the total number of subsets of $B$, then the value of $m \times n$ is

- [JEE MAIN 2020]

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

$\varnothing \in A$

Write the following sets in roster form :

$\mathrm{E} =$ The set of all letters in the world $\mathrm{TRIGONOMETRY}$

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

$\{\varnothing\} \subset A$