Answer: 7/20 of the laundry still needs to be washed
Explanation:
1. Find the gcf (greatest common factor) of 2/5 and 1/4, the greatest common factor of both 5, and 4, is 20.
2. Now, we have to use the 20, and rewrite the numbers. The 2/5 can be written as 8/20, and the 1/4 can be written as 5/20.
3. if Ms. Jones has washed 8/20 of the laundry, and her son has washed 5/20 of it, together they have washed 13/20 of it.
4. 20-13=7, so 7/20 of the laundry still needs to be washed.