Add 10 to the numerator of (5/7), how much should be added to the denominator to keep the fraction constant
在(5/7)的分子上加上10，要使分数大小不变，分母应加上多少
<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<gadget id="calculator">21 - 7</gadget>
<output>14</output>

<result>14</result>