Slope is often described as "rise over run." It indicates the vertical change of a line over a horizontal distance. If you set the rise over the run, you get a fraction that describes the slope. Sometimes this fraction can be further simplified by dividing the numerator and the denominator by their greatest common factor. This is the highest number that will divide evenly into both terms.
Determine the greatest common factor of both numbers in the fraction. If you are unsure what this is, write down the factors of both numbers and select the highest one that they have in common.
Divide the numerator by this number. If the result is zero, the simplified slope of the line is also zero.
Divide the denominator by the greatest common factor. If the result is one, drop the denominator and express the numerator as a whole number.