Here is the new description with all links and additional text removed: Learn how to add and subtract fractions whose denominators are not the same. Recall that when we want to add or subtract ...

Subtract the integers and subtract the fractions. When the fraction to be subtracted is bigger than the first fraction, change the mixed numbers to improper fractions first then do the subtraction.

In adding and subtracting fractions with unlike denominators, you have to get a least common denominator which is exactly like the least common multiple it just so happens to be in the denominator.