It take 23 mins for the drive
He needs to reach the airport by a quarter before 6
a quarter before 6 = 5.45
So he needs to leave 23 mins before 5.45
23 mins before 5.45 = 5.22
To change 5/6 to a fraction with a denominator of 12, you need to do one step. Since 12 is a multiple of 6 (meaning that it can be multiplied by 6 and another number), you multiply 5/6 by 2 to get 10/12. 10/12 is your answer.
