"Hey Mom? This question says 'Write 87 in the vigesimal system' and I put four score plus 7. But the answer in the book says 47. Do I have to count it wrong?"
"Yes, if you got it wrong, it's wrong."
"Yeah but, four score plus 7 is the same as 87, so technically I got it right. Do I have to have the same exact answer as the book?? Because four score plus 7...see? It's the same."
"No, it isn't. Four score is four times 20. That's 80. Plus 7 is 87. Eighty-seven and forty-seven aren't the same."
"I know, so 87 is the same as four score plus 7. You don't understand."
"If you wrote the number 47 in the base twenty system, then yes, it would equal 87. But the question was asking what 87 would equal if you wrote it in the base twenty system. That would be 47. Four score plus 7 does not equal 47. So your answer is wrong. If you'd written TWO score plus 7, then maybe..."
"But I basically got the same answer as Fred. SO it isn't wrong."
"No...YOU basically got 87 and HE basically got 47. They're not the same number, you know."
"Well, in this case, they are."
"You're telling me you'd be ok with me giving you 47 dollars in exchange for 87 dollars?? Cause I'd be happy to swap some money with you."
"I'm telling you...I don't want to do any more math today. Can I just be done??"
"Do 47 more problems and we'll see."