Question

Classify the following sets into empty set, finite set and infinite set. In case of (non-empty) finite sets, mention the cardinal number.
{x : x =5n, n $\in$ W and x<60}

Answer 1

$\{x:x=5n,n\in W$ and $x<60\}$
$=\{5,10,15,20,25,30,35,40,45,50,55\}$
It is finite set and it has $12$ elements