Xiaohua is 4 years younger than her sister this year, and her sister is exactly three times as old as Xiaohua. How old is Xiaohua this year?
小华今年的年龄比姐姐小4岁，姐姐的年龄正好是小华的3倍，小华今年多少岁．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

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

<result>2</result>