If $A$ and $B$ are not disjoint sets, then $n(A \cup B)$ is equal to
$n(A) + n(B)$
$n(A) + n(B) - n(A \cap B)$
$n(A) + n(B) + n(A \cap B)$
$n(A)\,n(B)$
If $A=\{3,6,9,12,15,18,21\}, B=\{4,8,12,16,20\},$ $C=\{2,4,6,8,10,12,14,16\}, D=\{5,10,15,20\} ;$ find
$C-B$
Show that for any sets $\mathrm{A}$ and $\mathrm{B}$, $A=(A \cap B) \cup(A-B)$ and $A \cup(B-A)=(A \cup B).$
If $A$ and $B$ are two sets, then $A \cup B = A \cap B$ iff
State whether each of the following statement is true or false. Justify you answer.
$\{2,6,10\}$ and $\{3,7,11\}$ are disjoint sets.
Which of the following pairs of sets are disjoint
$\{a, e, i, o, u\}$ and $\{c, d, e, f\}$