Which of the following sets is finite or infinite?
The set of prime numbers less than $99$.

Show that if $A \subset B$,then $(C - B) \subset (C - A)$.

Which of the following pairs of sets are equal? Justify your answer.
$X$,the set of letters in "$ALLOY$" and $B$,the set of letters in "$LOYAL$".

If $A$ and $B$ are two sets,then $A \cup (A \cap B)$ is equal to

Determine the subset for the set $\{n(n+1)(2n+1) : n \in \mathbb{Z}\}$.

Which of the following pairs of sets are equal? Justify your answer.
$A = \{ n : n \in \mathbb{Z} \text{ and } n^2 \le 4 \}$ and $B = \{ x : x \in \mathbb{R} \text{ and } x^2 - 3x + 2 = 0 \}$.