Which of the following are sets ? Justify your answer.

A collection of novels written by the writer Munshi Prem Chand.

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

$\{ x:x$ is a student of class $\mathrm{XI}$ of your school $\}  \ldots \{ x:x$ student of your school $\} $

Are the following pair of sets equal ? Give reasons.

$A = \{ 2,3\} ,\quad \,\,\,B = \{ x:x$ is solution of ${x^2} + 5x + 6 = 0\} $

In the following state whether $A=B$ or not :

$A=\{a, b, c, d\} ; B=\{d, c, b, a\}$

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

$1 \subset A$

Write down all the subsets of the following sets

$\{ a\} $