Let $A = \{1, 2, 3, 4, 5, 6\}$. Insert the appropriate symbol $\in$ or $\notin$ in the blank space:
$0 \dots A$

What universal set $(U)$ would you propose for the set of right triangles?

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 $B = \{ x : x \in \mathbb{R} \text{ and } x^2 - 3x + 2 = 0 \}$.

If a set $A$ has $n$ elements,then the total number of subsets of $A$ is

Determine whether the following set is finite or infinite:
The set of positive integers greater than $100$.

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