To help Briella remember the formula for slope, the best explanation would be:
"Slope is the ratio of rise over run. When given two points, you can determine the rise by finding the difference between the y-coordinates. You can determine the run by finding the difference between the x-coordinates."
This explanation correctly defines slope as the ratio of rise (the change in y) over run (the change in x), and it clearly describes how to calculate both rise and run using the coordinates of the two points.