If a person bikes 5 miles in 1.5 hours, how far can he bike in 13.5 hours

Using proportions is the easiest way to solve these type of questions. Proceed as such:

                     5 miles    =      'x' miles   
                   1.5 hours        13.5 hours

                       'x' miles = (5 miles / 1.5 hours) * (13.5 hours)

                       'x' miles = 45 miles