I borrowed 500 yuan from my father, 500 yuan from my mother, and used 970 yuan to buy a pair of shoes. The remaining 30 yuan, I returned 10 yuan to my father and 10 yuan to my mother, I owe my father 490, I owe my mother 490490 plus 490 = 980 plus my own ten = 990. Where are the other ten?

I borrowed 500 yuan from my father, 500 yuan from my mother, and used 970 yuan to buy a pair of shoes. The remaining 30 yuan, I returned 10 yuan to my father and 10 yuan to my mother, I owe my father 490, I owe my mother 490490 plus 490 = 980 plus my own ten = 990. Where are the other ten?

This problem can be easily solved by elementary school mathematics: borrow money for entry + 500 + 500 = 1000 spend money for account: - 970 = 30 repay money for account: - 10-10 = 10 balance for positive assets: 10 debt for negative assets: - 490-490 = - 980 assets: - 980 + 10 + 970 (shoes) = 0 the problem itself is a thinking trap, the key to solve is not