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

$\{ x:x$ is a triangle in a plane $\}  \ldots \{ x:x$ is a rectangle in the plane $\} $

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

$ 5\, .......\, A$

$A = \{ x:x \ne x\} $ represents

Write the following intervals in set-builder form :

$\left[ {6,12} \right]$

State whether each of the following set is finite or infinite :

The set of letters in the English alphabet

Write down all the subsets of the following sets

$\{ a,b\} $