Write down the fraction.
Choose a number that will divide into the numerator and denominator equally. If you choose the largest number that fits into both, you are using the greatest common factor. It is ideal to use the greatest common factor because it will reduce your work later. For example, if you have 20/30, you would choose 10 as the greatest common factor.
Divide the numerator and denominator by the greatest common factor. In this example, you would divide 20 and 30 by 10 to get the simplified fraction 2/3.
Continue dividing if you did not begin with the greatest common factor. For instance, if you chose to divide 20/30 by 5, you will end up with 4/6. This fraction is not in simplest form because both numbers can be divided evenly by 2. Therefore, you would divide again by 2 to get 2/3.