"Rise over Run" is your slope form. So if you draw these two points out on a graph, you'll see:
a) your rise is the distance of the Y points, or in this case 10 and
b) your run is the distance of the X points, or in this case 2.
Since the graph goes from bottom left to upper right, it's a positive slope. So you're slope is 10/2 or 5. Throw an "x" in front and you get 5x as your slope.
But wait, you're not done. Since it has to be in y=mx+b form and you've only figured out the "mx" piece, you need to find the "b". Fortunately if you continue to trace out the graph you'll see the y intercept should be at (0,-15).
Therefore your point slope form for this equation should be y = 5x - 15.
Graphing it out will always help you see better the graph and what the potential equation may look like. Hope this helped! Please don't hesitate if you need further assistance - I can help out through video conference. Good luck!
