Time taken to drive to her grandparents house = 6 5/6 hours
We convert this mixed into improper fraction, we get = 41/6 hours
Time taken to drive to her grandparents house = 41/6 hours
Time taken to drive back = 8 2/9 hours
We convert this mixed into improper fraction, we get = 74/9 hours
Time taken to drive back = 74/9 hours
Difference between the two = 74/9 - 41/6 = (148-123)/18 = 25/18 hours = 1 7/18 hours
Therefore it took 1 7/18 hours longer to drive back.
