What was the question for this implicit rationale, and corresponding answer?
The craft store made 36 / 3 = 12 sales in the fabric section. It made 36 / 4 = 9 sales in the jewelry section. Thus, there were 36 - 12 - 9 = 15 sales in the stationery section.
 The answer: 15
The question: A craft store makes a third of its sales in the fabric section, a quarter of its sales in the jewelry section, and the rest in the stationery section. They made 36 sales today. How many sales were in the stationery section?