Let $m, n \in \mathbb{N}$. If $n$ is divisible by $m$, then $m \le n$.
So far I have:
Let $m,n \in \mathbb{N}$ and assume that $n$ is divisible by $m$. Therefore, there exists $j \in \mathbb{Z}$ such that $n=jm$. By Proposition 2.11 (in the text our class uses), $j \in \mathbb{N}$. Therefore, by Proposition 2.21, $j \ge 1$.
Any help would be greatly appreciated, I don't even know if I'm going in the right direction here.