How do you add and subtract unlike mixed numbers?

Mixed numbers that have different denominators are called unlike mixed numbers. Before adding or subtracting unlike mixed numbers, they need to be changed to improper fractions with the least common denominator.

Example:

To subtract unlike mixed numbers:

At lunch, gallons of lemonade and gallons of iced tea were served. Find how many more gallons of lemonade were served.

First, change each mixed number to an improper fraction.
Find the numerator of the improper fraction by multiplying the denominator by the whole number, and then adding the numerator. The denominator is the same as in the mixed number.

Since and have different denominators, make equivalent fractions with the least common denominator. The least common denominator is the smallest number that both denominators can divide into evenly.

The smallest number that both 2 and 10 can divide into evenly is 10, so 10 is the least common denominator. Write the least common denominator as the denominator of both equivalent fractions.