Here’s a puzzle that took Bill Gates several hours to solve, but he stuck with it and finally got it.
The name of the game is Petals Around the Rose. The name is significant. Every answer is zero or an even number. That’s all the information you get.
It took me about five minutes to figure it out. I started getting way to complex, then reread the instructions and realized I was making it too complicated.
Caution: Some people give away the answer in the via link.