If 8 is added to the numerator of (4/15), how much should be added to the denominator to keep the size of this fraction unchanged.
如果(4/15)的分子加上8，要使这个分数的大小不变，分母应该加上多少．
<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<gadget id="calculator">45 - 15</gadget>
<output>30</output>

<result>30</result>