Xiaohua is 9 years old this year, and her mother is 33 years old this year. After many years, her mother's age will be three times Xiaohua's age.
小华今年9岁，妈妈今年33岁，再过多少年，妈妈的年龄是小华年龄的3倍．
<gadget id="calculator">33 - 9</gadget>
<output>24</output>

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

<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<gadget id="calculator">12 - 9</gadget>
<output>3</output>

<result>3</result>