We have the following:
The first thing is to transform the mixed numbers to decimal numbers, in the following way:
a.
to calculate the remaining time we must subtract the times where music is heard from 6 hours
Therefore, the answer is 2.5 hours or 5/2 hours battery remaining
b.
To calculate the fraction we must calculate that it represents 2.5 or 5/2 hours in the total, that is, 6 hours
The diagram is: