The question gives you unneeded information to confuse you: the length of the table. Just ignore that for this question.
To figure out how long he worked, add the time he spent each day on the table.
He spent 3 hours and 45 minutes the first day and 2 hours and 10 minutes the second day
3 hours + 2 hours = 5 hours
45 minutes + 10 minutes = 55 minutes
Herman spent 5 hours and 55 minutes to build the table.