The numerator of (2/5) is increased by 2, how much must be added to the denominator to keep the size of the fraction constant
(2/5)的分子增加2，要使分数的大小不变，分母必须要加上多少
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 - 5</gadget>
<output>5</output>

<result>5</result>