State which of the following sets are finite or infinite:
$\{ x:x \in N \text{ and } x^2 = 4 \}$

Write the following as intervals: $\{ x:x \in R, 3 \le x \le 4 \}$

In each of the following,determine whether the statement is true or false. If it is true,prove it. If it is false,give a counterexample.
If $A \not\subset B$ and $B \not\subset C$,then $A \not\subset C$.

If $A = \{ 1, 2, 3, 4, 5 \}$,then what is the number of proper subsets of $A$?

If ${N_a} = \{an : n \in N\}$,then ${N_5} \cap {N_7} = $

The solution set of $x \equiv 3 \pmod{7}$,where $p \in \mathbb{Z}$,is given by: