Answer:
Eight cups of yogurt will be used.
Explanation:
Let cups of yogurt used in 12 cups of smoothies be x
Cups of juice used in 12 cups of smoothies = 12- x
The ratio of yogurt to juice is 2 cups to 1 cup that is:

Ratio will be maintained through out 12 cups of smoothies:



x = 8
Eight cups of yogurt will be used.