I borrowed 500 yuan from my father, borrowed 500 yuan from my mother, bought a pair of leather shoes and used 970 yuan, left 30 yuan, returned 10 yuan to my father, returned 10 yuan to my mother, and owed 490 yuan to my father. Mom 490, 490+490=980, plus my own 10 yuan=990 yuan, where did the other 10 yuan go?
向爸爸借了500元，向妈妈借了500元，买了双皮鞋用了970元，剩下30元，还爸爸10块，还妈妈10块，自己剩下了10块，欠爸爸490，欠妈妈490，490+490=980，加上自己的10块=990元，还有10块去哪里了呢？
<gadget id="calculator">490 + 490 + 10</gadget>
<output>990</output>

<result>990</result>