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

$D-C$

Let $A$ and $B$ be two sets in the universal set. Then $A - B$ equals

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 $X=\{a, b, c, d\}$ and $Y=\{f, b, d, g\},$ find

$Y-X$

Find the intersection of each pair of sets :

$X=\{1,3,5\} Y=\{1,2,3\}$

If $A=\{3,5,7,9,11\}, B=\{7,9,11,13\}, C=\{11,13,15\}$ and $D=\{15,17\} ;$ find

$A \cap D$