Answer: 15 fifths.
Explanation:
If we divide one bulletin board in five parts , then each part represents one-fifth of the the bulletin board.
Recall it, One bulletin board = 5 parts
Then, 3 bulletin board = 5=5+5 =15 parts
That mean 3 bulletin boards has 15 fifths.
Hence, there are 15 fifths in one bulletin board.
To show this we can the make the model shown in below.