Answer: I think the answer is 7
Explanation:
to get the answer i divided 108(photos) by 9 (rolls used) to get the number of how many pictures I can take with 1 roll (it gave me 12) the I divided 84 by the number of photos you can take with 1 roll (12) it gave me 7(rolls) and that is how I got the final answer.
I hope I have help. Have a nice day