A day has 24 hours.
The clock loses 5 minutes every 24 hours.
2 hours is 1/12 of 24 hours, so in 2 hours, the clock loses 1/12 of 5 minutes.
1/12 * 5 minutes = 5/12 minutes
5/12 minutes * 60 seconds/minute = 25 seconds
In 2 hours, the clock loses 5/12 minute which is 25 seconds.