This year, Teacher Wang's age is four times that of Xiaoxiao's. Twenty years later, Teacher Wang's age is exactly twice that of Xiaoxiao's. How old is Xiaoxiao this year?
今年，王老师的年龄是笑笑年龄的4倍，20年后，王老师的年龄正好是笑笑的两倍，笑笑今年多少岁？
<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<gadget id="calculator">40 - 20</gadget>
<output>20</output>

<gadget id="calculator">4 - 2</gadget>
<output>2</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<result>10</result>