Alice was walking on the street when she came across a man playing with a die. She could not help trying to check if the die was loaded and while she was concluding that it wasn't loaded, the man noticed her and started talking:
Hey madam, wanna play a game? It's simple, in a round you roll the die any number of times, add the results, and I give you the amount of money you scored. But I need to get some interest in that too, so you give me 10 for each round and if your sum is over 13, I give you nothing back. Wanna give a try?
Do you think Alice should play this game? What is the optimal strategy that she can use?
Answer is a strategy and its average score. Of course, as you brain is not as sharp as Alice's you can use computers to help you.
EDIT: A round is a succession of any number of dice roll until Alice decides to stop or is strictly over 13. Source: diophante.fr