During the first hour, they practiced for 5/8 of an hour. During the second hour, they practiced for 2/3 of an hour. This means that the total time for which they practiced in the first 2 hours would be
5/8 + 2/3 = 31/24 hours
During the last two hours, they first practiced for 3/5 of an hour, took a 1/2 hour break and then practiced the rest of the time. This means that the rest of the time for which they practiced is
2 - (3/5 + 1/2) = 2 - 11/10 = 9/10
Therefore, the time they spent practicing in total would be
