Take the fractions and make them so the bottom number is the same. So you would take 2/3 and multiply them by 5/5 and 1/5 by 3/3 so you would get 10/15 and 3/15. Add those fractions together and you get 13/15 so it would be 4 13/15 cups or if you want to simplify it then it would be 4 2.6/5