Answer: 220
Step-by-step explanation
Given info:
- 500 people surveyed.
- 216 gave blood.
- 152 helped set up, clean up, etc.
- 88 gave blood and did clean up.
From that we can write
- 216-88 = 128 people gave blood only, but didn't give extra help.
- 152-88 = 64 people helped out, but didn't give blood.
Therefore, 128+64+88 = 280 people either gave blood, did clean up/extras, or both. This must mean 500-280 = 220 people did neither event. This is the final answer.
Below is a venn diagram to visually organize the data. The value 220 marked in red is outside both bubbles, but it is still inside the universal set. The universal set is the set of everyone surveyed.