Consider the question. On a particular week, Fatima's restaurant served 25 people food and drinks, and 3/5 of that number came to buy coffee. How many people did not buy coffee in the restaurant?
 If the answer is '10'; explain the reasoning:
The number of customers who were served coffee in the restaurant is 3 / 5 * 25 = 15. If the total number of customers who came to the restaurant was 25, then 25 - 15 = 10 customers did not buy coffee.