Let's say that a 14-ounce cup of coffee is 20 percent milk. If you add 7 ounces of coffee, what is the percentage of milk in the new mixture?

Alright, 14 oz. cup of coffee contains 20% milk. If you add 7 ounces to that mixture, your answer would be:

14 oz = 0.2 milk

+7 oz. = 28

28/14 = 2

0.2*2 = 0.4, written as a percent will be 40%

40% milk.