If $A$ and $B$ are disjoint, then $n(A \cup B)$ is equal to
$n(A)$
$n(B)$
$n(A) + n(B)$
$n(A)\,.\,n(B)$
Let $A=\{1,2,3,4,5,6\}, B=\{2,4,6,8\} .$ Find $A-B$ and $B-A$
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
$A-C$
If $A=\{3,5,7,9,11\}, B=\{7,9,11,13\}, C=\{11,13,15\}$ and $D=\{15,17\} ;$ find
$\left( {A \cup D} \right) \cap \left( {B \cup C} \right)$
If $A=\{3,5,7,9,11\}, B=\{7,9,11,13\}, C=\{11,13,15\}$ and $D=\{15,17\} ;$ find
$A \cap C$
Which of the following pairs of sets are disjoint
$\{1,2,3,4\}$ and $\{ x:x$ is a natural number and $4\, \le \,x\, \le \,6\} $