Final answer:
Both stores must have 15 customers before the total amount of money they have is equal. To find the number of customers both stores must have before their total amount of money is equal, we need to consider the average amount of money spent per customer.
Step-by-step explanation:
If both stores see the same number of people but have different prices for their items, the total amount of money they have may differ. Let's say store A has 10 customers and each customer spends $5, while store B has 15 customers and each customer spends $3. Store A would have $50 (10 customers x $5) and store B would have $45 (15 customers x $3). In this case, store A has more money.
Thus, we need to find a scenario where both stores have an equal total amount of money. One such scenario could be if both stores have 15 customers. If store A has 15 customers and each customer spends $3, the total amount of money would be $45. If store B also has 15 customers and each customer spends $3, the total amount of money would also be $45. Therefore, the answer is D) 15 customers.