Uncle is 20 years older than Xiaohua. Next year, uncle will be three times Xiaohua's age. How old is Xiaohua this year?
叔叔比小华大20岁，明年叔叔的年龄是小华的3倍，小华今年多少岁？
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

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

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<result>9</result>