Rise over Run.
Understanding y = mx + b.
Descartes invented the coordinate plane while watching a fly on his ceiling.
m is the move (slope), b is the begin (y-intercept).
Plain English: Every straight line can be described by two things: Where it starts (b) and how steep it is (m). Positive slope goes up hill, negative slope goes down hill.
Real-world example: Road grades (steepness), Roof pitches, Economy trends.
Mixing up x and y when calculating rise over run. Slope is Change in Y divided by Change in X.