Question

Let A = { $x:xϵN,$ x is a multiple of 3\)} and

B = {$x:xϵN$ and x is a multiple of 5}. Write $A\cap B$.

Answer 1

$A\cap B$ = {$x:xϵN,xϵAandxϵB$}

= {$x:xϵN,$ x is a multiple of 3 and x is a multiple of 5}

= {$x:xϵN,$x is a multiple of 15 }