What a tough question!
Between each strike of the bell there is an interval of time when the bell is swung from one side to another
We won’t count the time it takes to swing the bell before the first strike and after the last since we don’t hear anything, it won’t be included in the 5 second interval
5 strikes are made up of 4 intervals between them
4 intervals = 5 seconds
1 interval = 5/4 seconds
12 strikes have 11 intervals between them
11 * 5/4 = 55/4
Hope this helps!