Show that the set of letters needed to spell $"\mathrm{CATARACT}"$ and the set of letters needed to spell $"\mathrm{TRACT}"$ are equal.
Which of the following are sets ? Justify your answer.
The collection of all even integers.
Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?
$\{1,2,3\}\subset A$
Which of the following are sets ? Justify your answer.
A collection of most dangerous animals of the world.
State whether each of the following set is finite or infinite :
The set of letters in the English alphabet