The answer to the 6/8 minute car cleaning math problem discussed in the episode is not "there might not be one right answer." Assuming constant rates of car cleaning, the answer is that it will take both parties 24/7 minutes to clean a single car, or approximately 3 minutes and 25 seconds.
The car wash question is revisited on Girl Meets World. And just like this episode, Minkus (Farkle), gets it wrong using math and can't understand why.
The name of the restaurant Amy and Alan sneak away to is "La Bugia", which is Italian for "the lie". Kind of an appropriate inside joke.