Add 15 to the numerator of (3/8), how much should be added to the denominator to keep the original fraction unchanged
把(3/8)的分子加上15，要使原来分数大小不变，分母应加上多少
<gadget id="calculator">3 + 15</gadget>
<output>18</output>

<gadget id="calculator">18 / 3</gadget>
<output>6</output>

<gadget id="calculator">6 * 8</gadget>
<output>48</output>

<gadget id="calculator">48 - 8</gadget>
<output>40</output>

<result>40</result>