For this problem you would have to convert the 1/4 and 2/5 into fractions with the same denominator. This way you get 1/4 = 5/20 and 2/5 = 8/20. Now you can see that THE SON MOWED MOST OF THE LAWN. For the next part you would add the 5/20 + 8/20 = 13/20, which shows that 13/20 of the lawn was mowed. The whole lawn is 20/20, so all you have left to do is subtract, 20/20 - 13/20 = 7/20. NOW YOU CAN SE THAT THERE IS 7/20 LEFT OF THE LAWN TO MOW.
