Since 1 hour is 60 minutes, 20 minutes is 20 / 60 = 1 / 3 of an hour. Eating 3 potatoes per 20 minutes is 3 / (1 / 3) = 9 potatoes per hour. At 9 potatoes per hour, it will take Jason 27 / 9 = 3 hours to eat all of the potatoes.
This justifies what answer for what question? Q & A:
If Jason eats three potatoes in 20 minutes, how long, in hours, would it take for him to eat all 27 potatoes cooked by his wife?
3