The diagram shows the graph of $y=|mx+n|$

(i tried my best to do the same thing as my exercise book, actually 1 is propotional to 1 and 3 is propotional to 3, but 2 is not propotional to 2)
Find the value of $m$ and $n$.
Anyone can help me solve this problem? Thanks

Hints: What value inside the absolute value sign can make $y=0$? If you set $x=0$, what is $y$?