Write the addition sentence. For instance, you might have 2 1/2 + 4 3/5.
Add the whole numbers. In this example, you would add 2 and 4 to get 6.
Add the fractions. In this example, you would add 1/2 and 3/5. When you add fractions, the denominators must be the same. Therefore you must find a common denominator, which is a number into which both denominators will divide evenly. In this case, 2 and 5 will divide into 10. Since you have to multiply 2 by 5 to get 10, multiply 5 times the numerator in the first fraction to get 5. In the second fraction, you have to multiply 5 times 2 to get 10, so you multiply 2 times the numerator, which gives you 6. Now you can add 5/10 + 6/10 to get 11/10.
Convert your answer to a mixed number if necessary. Since 11 is larger than 10 in the example, you would divide 10 into 11 to get a mixed number of 1 1/10.
Add the mixed number to the previous total that you found when adding the whole numbers. In this example, you added 2 and 4 to get 6. Add 1 1/0 to 6 to get 7 1/10 as your final answer.