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

$B \cap C$

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

$A-B$

Let $P=\{\theta: \sin \theta-\cos \theta=\sqrt{2} \cos \theta\}$ and $Q=\{\theta: \sin \theta+\cos \theta=\sqrt{2} \sin \theta\}$ be two sets. Then

Let $A=\{1,2,3,4,5,6,7,8,9,10\}$ and $B=\{2,3,5,7\} .$ Find $A \cap B$ and hence show that $A \cap B = B$

If $A, B$ and $C$ are any three sets, then $A -(B  \cup C)$  is equal to