> "If you are drinking alcohol, then you must be over 18" This is different, and much easier problem. You don't need to care about the non-alcoholic beverages

> "If you are drinking alcohol, then you must be over 18" This is different, and much easier problem. You don't need to care about the non-alcoholic beverages in this scenario, so it's more intuitive. The less intuitive aspect of the original scenario is that you need to care about all the colored patch sides because you need to know that there's not a multiple of 4 on the non-yellow cards. If you rephrased the question such that the proposition is "which cards do you flip to determine that the people over 18 are only drinking alcohol and people under 18 aren't" then it's a lot less intuitive and probably more likely to trip people up.