Answer:
zero
Step-by-step explanation:
I remember it as: whenever you have 0 first in the expression, the answer is 0.
So, if you tried to graph 0/90 using rise over run, it would be a horizontal straight line, so there would be no slope - 0.
If you tried to graph 90/0, it would be a vertical line because you can't tell what slope it has - undefined slope.
I hope that helps.
