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

$C-B$

Let $A=\{1,2,3,4,5,6\}, B=\{2,4,6,8\} .$ Find $A-B$ and $B-A$

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

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

$X \cap Y$

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

$A-D$

Show that the following four conditions are equivalent:

$(i)A \subset B\,\,\,({\rm{ ii }})A - B = \phi \quad (iii)A \cup B = B\quad (iv)A \cap B = A$