You have to cross the river with one boat that has 2 seats. One for you and one for the lion, monkey and bananas. You can only take one at a time.
Remember the lion will eat the monkey and the monkey will eat the bananas if they're left alone.
Solution #1
1) Take the monkey2) Come back
3) Take the lion
4) Bring the monkey back
5) Take the bananas (lion and bananas are on the other side and the lion won't eat the bananas)
6) Come back
7) Take the monkey
Solution #2
1) Take the monkey2) Come back
3) Take the bananas
4) Bring the monkey back
5) Take the lion (lion and bananas are on the other side and the lion won't eat the bananas)
6) Come back
7) Take the monkey