In this math tutorial the instructor shows us how to add three fractions with common denominators. He says that it is similar to adding two fractions with common denominator. He tells us first to add all the numbers in the numerator which gives us a new number which is the numerator in our answer and the denominator to our answer is the original common denominator. Now, if the resulting fraction is improper fraction, you will have to convert it into a mixed number. In this video the author shows how to add three fractions with common denominator.