Answer:
15.15% probability that Neil selects a bone and then a ball
Explanation:
A probability is the number of desired outcomes divided by the number of total outcomes.
Initially, there are 3+4+5 = 12 treats. 4 of those are bones. So the probability of selecting a bone is 4/12 = 1/3.
Now suppose a bone has been selected. Now there are 11 treats, 5 of which are balls. So the probability of selecting a ball in this situation is 5/11.
What is the probability Neil selects a bone and then a ball?

15.15% probability that Neil selects a bone and then a ball