I borrowed 500 yuan from my father and 500 yuan from my mother. I spent 970 yuan to buy a pair of leather shoes, and 30 yuan was left. I returned 10 yuan to my father and 10 yuan to my mother, which means I still owe my father 490 yuan and my mother 490 yuan. 490+490=980 yuan, which means you borrowed 490 from your father and 490 from your mother. Because we each paid back 10 yuan, not borrowed 500 yuan.

Calculation: Dad borrows 490 and Mom borrows 490. 490+490=980 yuan (total loan), which 970 yuan used to buy shoes. So there is 10 yuan left. It is normal. There is no other 10 yuan.

The misunderstanding of this question is that your 10 yuan is borrowed from your parents. It is meaningless for you to borrow 490+490+ 10 yuan, because this 10 yuan is included in 490+490.