Hi there!
The answer is 18000
Method: 5-----1500
60-----x
Since there is a direct proportion, you just have to multiply the number of attendees there will be (in this case 60) times the total amount of money raised (1500), and once you have this result, you just simply divide it by the amount of attendees it took to raise the money.
This is called a rule of 3.
Hope this helps!