A
B
C
D
Explanation
Correct answer: A.
Choice A is correct. It's given that a total of people contributed to a charity event as either a donor or a volunteer. It's also given that people contributed as a donor. It follows that , or , people contributed as a volunteer.
Desmos solution:
Enter in Desmos:
Reviewed and rewritten by CookSAT
Why the other choices are wrong
Choice B
Choice B is incorrect. This is the number of people who contributed as a donor, not a volunteer.
Choice C
Choice C is incorrect. This is the total number of people who contributed as either a donor or a volunteer, not the number of people who contributed as a volunteer.
Choice D
Choice D is incorrect and may result from conceptual or calculation errors.