Explanation:
It sounds like you need to find your slope. The equation is y2-y1/x2-x1
Say you have two points, and those two points make a line.
Say those points are (0,0), and (5,5).
To find the slope, we need which is equal to x2-x1/y2-y1 (the two coordinates for the points) which in this case, equals one. That means the constant rate of going up is, 1 each time it moves to the left once.
I hope this answers your problems. If you don't understand anything, I can try to help in the comments!