You are adding both fractions together to determine the total of the floor they both cleaned in all.
so 2/7 + 3/7 =
To add fractions, you need both denominators to be the same. In this case, they are already the same so you don't need to adjust the fraction before adding them.
Now all you need to do is to add the numerators together so
2 + 3 = 5
So you put the numerator total over the common denominator.
* You do not add the denominators, only the numerators.
