Multiply the denominator of (3/4) by 3, how much should be added to the numerator to keep the fraction size unchanged
(3/4)的分母乘以3，要使分数大小不变，分子应加多少
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">9 - 3</gadget>
<output>6</output>

<result>6</result>