It takes the earth 24 hours to complete a full rotation. it takes mercury approximately 58 days, 15 hours, and 30 minutes to complete a full rotation. how many hours does it take mercury to complete a full rotation?

To answer this question you need to convert the mercury rotation time from 58 days, 15 hours, and 30 minutes into hours. 
First, try to convert the days into hours. The calculation would be=
58 days x 24 hours/day= 1392 hours.
Then convert the 30 minutes into the hours. 
30 minutes / (60 minutes/hour)= 0.5 hours

After that you just need to add them all, then hours need for mercury to complete a full rotation: 1392 hours + 15 hours+ 0.5 hours= 1407.5 hours.