A recipe that makes 6 servings calls for 1/2 cup of butter. Nancy modifies the recipe so that it can serve 8

How many cups of butter does Nancy need?

6 servings ... 1/2 cup of butter

8 servings ... x cup of butter

We would like to know what is the value of the x.

6 * x = 8 * 1/2

6 * x = 4 / 6

x = 4/6

x = 2/3

Result: Nancy needs 2/3 cup of butter for 8 servings.