Question

If $A=(6,7,8,9),B=(4,6,8,10)$ and $C=\{x:xϵN:2<x\le 7\}$ ; find : $n(B-(A-C\left)\right)$

Answer 1

$A=\{6,7,8,9\}$
$B=\{4,6,8,10\}$
$C=\{x:x\in Nand2<x\le 7\}$
$\therefore C=\{3,4,5,6,7\}$

$A-C=$ Contains elements present only in $A$ and NOT in $C$
$A-C=\{6,7,8,9\}-\{3,4,5,6,7\}$
$A-C=\{8,9\}$
$B-\{A-C\}=\{4,6,8,10\}-\{8,9\}$
$=\{4,6,10\}$

Hence, $n(B-(A-C\left)\right)=3$.