Why is that so? I borrowed 500 yuan from my father and 500 yuan from my mother. Then I bought a pair of shoes, used 970 yuan and left 30 yuan. I returned it to my father I returned 10 yuan to my father, 10 yuan to my mother, and 10 yuan to myself. In this way, I owe 490 yuan to my father, 490490 yuan to my mother, 490 yuan to my mother, and 10 yuan to myself. Where is the remaining 10 yuan?

Why is that so? I borrowed 500 yuan from my father and 500 yuan from my mother. Then I bought a pair of shoes, used 970 yuan and left 30 yuan. I returned it to my father I returned 10 yuan to my father, 10 yuan to my mother, and 10 yuan to myself. In this way, I owe 490 yuan to my father, 490490 yuan to my mother, 490 yuan to my mother, and 10 yuan to myself. Where is the remaining 10 yuan?

You owe your father 490, calculated as - 490, you owe your mother 490, calculated as - 490, you still have 10 yuan, calculated as + 10
（-490）+（-490) + 10 = -970
It's the money for the shoes