Final answer:
If there are 6 expired milk chocolates and 6 non-expired milk chocolates, then there are a total of 12 milk chocolates in the case.
Step-by-step explanation:
The question asks how many milk chocolates are expired if there are 6 milk chocolates that are not expired in a case that originally contains 15 chocolate bars of three varieties: milk, dark, and milk/dark mix. It was given that there are 6 expired milk chocolates. Therefore, if there are 6 milk chocolates that are not expired, the total number of milk chocolates in the case would be the sum of the expired and the non-expired milk chocolates, which is 6 expired + 6 not expired = 12 milk chocolates in total.