Today, I went shopping, 500 yuan from my father, 500 yuan from my mother, and bought a pair of shoes. I spent 970 yuan, 30 yuan left, 10 yuan for my father, 10 yuan for my mother, 10 yuan for myself, 490 yuan for my father, 490 yuan for my mother, 490 + 490 = 980. Plus 10 yuan for myself, 980 + 10 = 990, where's 10 yuan

Today, I went shopping, 500 yuan from my father, 500 yuan from my mother, and bought a pair of shoes. I spent 970 yuan, 30 yuan left, 10 yuan for my father, 10 yuan for my mother, 10 yuan for myself, 490 yuan for my father, 490 yuan for my mother, 490 + 490 = 980. Plus 10 yuan for myself, 980 + 10 = 990, where's 10 yuan

That's not right at all! You paid 20 for 980, shoes cost 970, and you have 10 yuan left. 980 is what you spend, 10 is what you have. They are not the same number, but one positive and one negative. It shouldn't be 980 + 10, it should be 980-10