For example, tell me:
* What is the tube made of? Is it a cardboard tube, a metal pipe, or something else?
* Where is the banana located in the tube? Is it at the bottom, the top, or somewhere in the middle?
* How are the monkeys positioned? Are they both outside the tube, or is one inside?
* What are the limitations? Are the monkeys able to use their hands or other tools?
Once I have more information, I can help you figure out how the monkey might get the banana!