Alright, lets get started.
Jen picked three fourth in half an hour.
Half an hour means 30 minutes.
At the same rate, how many she can pick in 2 hours.
2 hours means minutes
Now,
In 30minutes, Jen can pick =
In 1 minute, Jen can pick =
In 120 minutes, Jen can pick =
Hence Jen can pick complete 3 in 2 hours of time.
So the answer is 3 : Answer
Hope it will help :)