Question

Find the cardinal number of $A_4$ = {$b$ : $bϵZ$ and $-7<3b-1\le 2$}

Answer 1

Cardinal number of a set is the number of elements it has.
Given, $A_4$ = {$b$ : $bϵZ$ and $-7<3b-1\le 2$}
$-7<3b-1\le 2$
$\Rightarrow -6<3b\le 3$
$\Rightarrow -2<b\le 1$
Since $b$ is an integer, possible values of $b$ satisfying the above condition $=-1,0,1$
Hence cardinal number of the given set $=3$.