Xiaosi is 10 years old this year, and Xiaosi's mother is 35 years old. How many years later, her mother's age is twice that of Xiaosi.
今年小思10岁，小思的妈妈35岁，多少年后妈妈的年龄是小思的2倍．
<gadget id="calculator">35 - 20</gadget>
<output>15</output>

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

<gadget id="calculator">15 / 1</gadget>
<output>15</output>

<result>15</result>