OK. What are the known facts? We need 20 servings, and 1/3 cup is for 8. Let's move things around. Think as if 1/3 was for 5 people. That would mean you would need 1 1/3 cups for 20 servings. Because 5*4 is 20 and 1/3*4 is 1 1/3. Now for the extra 3. There are 4 sets of 3 total left, which is 12. 12 is 1 1/2 of 8, so we need 1/3 cup and half of 1/3. I don't want to give the entire thing away, so I will leave that for you to figure out! Bye :D
