Add 12 to the numerator of (4/9), to keep the size of the original fraction unchanged, the denominator should add ... how many
(4/9)的分子加上12，要使原分数大小不变，分母应加上…多少
<gadget id="calculator">4 + 12</gadget>
<output>16</output>

<gadget id="calculator">16 / 4</gadget>
<output>4</output>

<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<gadget id="calculator">36 - 9</gadget>
<output>27</output>

<result>27</result>