Xiaojun is 9 years old this year, and his mother is 37 years old. After many years, his mother's age will be three times that of Xiaojun's.
小军今年9岁，妈妈今年37岁，多少年后，妈妈的年龄是小军的3倍．
<gadget id="calculator">37 - 9</gadget>
<output>28</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">28 / 2</gadget>
<output>14</output>

<gadget id="calculator">14 - 9</gadget>
<output>5</output>

<result>5</result>