Add 14 to the numerator of (7/10), how much should be added to the denominator to keep the size of the fraction constant?
(7/10)的分子加上14，要使分数的大小不变，分母应加上多少？
<gadget id="calculator">7 + 14</gadget>
<output>21</output>

<gadget id="calculator">21 / 7</gadget>
<output>3</output>

<gadget id="calculator">10 * 3</gadget>
<output>30</output>

<gadget id="calculator">30 - 10</gadget>
<output>20</output>

<result>20</result>