He then went to see the oranges being harvested. He found out that they harvest 8 sacks per day. How many days will it take to harvest 24 sacks of oranges?
Let's denote the number of sacks of oranges per day by x. Then 8 sacks per day is x sacks per day. 

The number of days it will take to harvest 24 sacks of oranges is 

24/x days. 

Therefore the answer (numeric) is: 

24/x = 24/8 = 3