I believe the answer is x² + 3x - 10.
I found this on Yahoo Answers so it isn't my own work.
Answer:
3/15, 1/5, or 0.2 probability. Highly unlikely
Explanation:
12/15 is the shown probability. The leftover is 3/15, so 3/15 is the chance of missing the basket.
~Hope this helps~
