We add all these mixed numbers together:
1 1/2 + 2 3/4 + 2 1/3
It will be easier to convert the mixed numbers into improper fractions:
3/2 + 11/4 + 7/3
Now we have to find the common denominator which is 12:
18/12 + 33/12 + 28/12 = 79/12 = 6 7/12
The answer is 6 7/12 hours.