Answer:
The farmer had to do 27 loads.
Explanation:
Basically the easy way to do this is to grab a calculator (or the paper and pen way) and keep adding 336 until you get to 8914.
Once you add it all you will see there is a remainder of his corn left (that has not been delivered):178
Even though it isn't a full 336, the farmer would still have to make another trip.
336*26=8,736
So, adding the remainder into it's own load, we would get:
27.