Answer:
850
Explanation:
To get my answer, I divided 150 by 17. (The survey of people and the # of them under 21) I got 8.8235. Next, I divided 7500 (the total of people in the stadium) by 8.8235 (the decimal that I got above) I got 850.
To check my answer, I divided 7500 by 850 and got 8.8235, the same ratio as the survey.