The combined age of Xiaohong and her elder brother is 20 years old. My brother is 12 years old this year, how old is my brother older than Xiaohong?
小红和哥哥的年龄加起来是20岁．哥哥今年12岁，哥哥比小红大多少岁？
<gadget id="calculator">20 - 12</gadget>
<output>8</output>

<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<result>4</result>