First, let's change 4 1/3 into a mixed number. In 4, there are 4 x 3 = 12 thirds.
Add the 1/3 to this and we get 13/3.
So 4 1/3 = 13/3
To find out how many 2/3 pound servings are in a 13/3 pound bag, find out how many 2s go into 13.
13 / 2 = 6.5
So 6 and a half of these servings OR 6 whole servings go into a 4 1/3 pound bag