Which of the following are sets ? Justify your answer.

The collection of all the months of a year beginning with the letter $\mathrm{J}.$

The collection of all months of a year beginning with the letter $\mathrm{J}$ is a well-defined collection of objects because one can definitely identity a month that belongs to this collection.

Hence, this collection is a set.

Write the following as intervals :

$\{ x:x \in R,0\, \le \,x\, < \,7\} $

Are the following pair of sets equal ? Give reasons.

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

If $Q = \left\{ {x:x = {1 \over y},\,{\rm{where \,\,}}y \in N} \right\}$, then

Which of the following are sets ? Justify your answer.

A team of eleven best-cricket batsmen of the world.

Examine whether the following statements are true or false :

$\{ 1,2,3\} \subset \{ 1,3,5\} $