Answer:
5 people
Step-by-step explanation:
21 people went to the fair and 9 people were on a stagecoach. The remaining 12 people rode the buggies. We know that 3 people were in each buggy, so there were 4 buggies (12÷3=4). On the return trip, 4 people rode each buggies, so there were a total of 16 people who rode buggies (4 people×4 buggies=16 people). The remaining 5 returned on a stagecoach (21-16=5).