The elder brother and the younger sister have 30 stamps in total. After the elder brother gives the younger sister 6 stamps, the number of stamps of the two is equal. How many stamps did the younger sister originally have?
哥哥和妹妹共有30张邮票，哥哥给妹妹6张后，两人的邮票张数相等，妹妹原来有多少张邮票．
<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">30 - 12</gadget>
<output>18</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<result>9</result>