First, I borrowed 500 yuan from my father, 500 yuan from my mother, bought a pair of shoes, spent 970 yuan, and left 30 yuan. The money here is still right. I paid my father 10 yuan and my mother 10 yuan, and there is still 10 yuan left. The money here is also right. It is logically right to owe your father 490 yuan and your mother 490 yuan, but it is wrong for you to work out 490+490+ your own 10 yuan =990 yuan. 490+490=980 yuan shows that you still owe them so much, because you have already paid back 20 yuan, and you have to take 980+20= 1000 yuan and your remaining 10 yuan. It should be calculated as follows: You spent 970 yuan and gave each of your parents 10 yuan, that is, 20 yuan, leaving 10 yuan.