Presumably you want the slope of a straight line.
If you are given the equation, put it into the form: y = mx + b.
Then m is the slope.
If you are given 2 points (x1,y1) and (x2,y2) then the slope is (y2 - y1)/(x2 - x1).
In words the slope is the change in the vertical direction divided by the change in the horizontal direction, sometimes called rise/run.