slope = rise/run
Rise is how far up or down you go from one point to another point.
Run is how far right or left you go from one point to another point.
Look at the figure.
First, look at lower left the blue point on the blue line.
To go from that point to the upper right point, you need to go up 2 units along the blue dashed line. That is a rise of 2.
Then where you see the red square, you go right along the red dashed line, and you go 4 units to the right. That is a run of 4.
slope = rise/run = 2/4 = 1/2
