اگر $A=\left\{ 3k\,\left| k\in W \right. \right\}$ و $B=\left\{ 2k-1\,\left| k\in \mathbb{N} \right. \right\}$ آن گاه $A-B$ برابر است با ...............
$\left\{ 6k\,\left| k\in W \right. \right\}$
2 )
$\left\{ 2k\,\left| k\in \mathbb{N} \right. \right\}$
3 )
$\left\{ 3k\,\left| k\in \mathbb{N} \right. \right\}$
4 )
A