You mow 1/3 of the lawn. Your sister mows 2/7 of the lawn. What fraction of the lawn is mowed?

13/21 of the lawn is mown.

Step-by-step explanation:

First, convert 1/3 to 7/21 by multiplying both the numerator and the denominator by 7. Then, convert 2/7 to 6/21 by multiplying both the numerator and the denominator by 3. Last, add 7/21 to 6/21 to get an answer of 13/21.

6/21 + 7/21 = 13/21 of the lawn was mowed?