Let $A = \{1, 2, 3, 4, 5, 6\}$. Insert the appropriate symbol $\in$ or $\notin$ in the blank space:
$10 \dots A$

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 $x \in A$ and $A \not\subset B$,then $x \in B$

State whether the following set is finite or infinite:
The set of numbers which are multiples of $5$.

If $A$ and $B$ are two sets,then $A \cup B = A \cap B$ if and only if

State which of the following sets are finite or infinite:
$\{ x : x \in \mathbb{N} \text{ and } (x - 1)(x - 2) = 0 \}$

Let $S = \{0, 1, 5, 4, 7\}$. Then the number of all subsets of $S$ is: