39 persons can repair a road in 12 days, working 5 hours a day. In how many days will 30 persons, working 6 hours a day, complete the work?

39 persons can repair a road by working 5 hours a day in 12 days.
1 persons can repair a road by working 5 hours a day in 12 x 39 days.
1 persons can repair a road by working 1 hours a day in 12 x 39 x 5 days.
30 persons can repair a road by working 1 hours a day in 12 x 39 x 5 / 30 days.
30 persons can repair a road by working 6 hours a day in 12 x 39 x 5 / 30 x 6 days.
30 persons can repair a road by working 6 hours a day in 2 x 39 x 5 / 30 days.
30 persons can repair a road by working 6 hours a day in 39 x 1 / 3 days.
30 persons can repair a road by working 6 hours a day in 13 days.