ANSWER
3
EXPLANATION
To answer this question we can make a Venn diagram. Each circle will represent the people who like dolphins and the people who like polar bears. We know that 3 people like both, so there are 3 people in the area shared by both circles. If 6 people like dolphins and 6 like polar bears, knowing that already 3 people are in the area shared by both circles, in the individual area of each circle there will be 3 people:
So, we can see that there are 3 people out of the 6 that like dolphins that also like polar bears.
Hence, there are 3 people that like dolphins but not polar bears.
