In this tutorial the author shows an easy and simple way of subtracting fractions with uncommon denominators. He says that to subtract fraction with uncommon denominator, we need to make their denominators equivalent first and after making the denominators equal, you need to increase the numerators proportionally to maintain the original ratio of the fraction. Now as the denominators are same, we can directly subtract the numerators arriving at a new fraction. He further shows how to deduce the fraction if it's possible. If you are looking for a math tutorial on subtraction fractions with uncommon denominators this is the tutorial for you.