Answer: 17/27
How to get this answer:
Add up the values in either the drama circle or the athletics circle
51+15+12+11+108+7 = 204
There are 204 students in drama, athletics, or both.
You didn't post this info, but the last problem stated there were 324 juniors total. Assuming this is still the case, we would have a probability of 204/324 which reduces to 17/27. I divided both parts of the first fraction by the greatest common factor 12.
note: 17/27 = 0.6296 approximately