The numerator of (2/5) becomes 6, what should be the denominator to keep the fraction size constant.
(2/5)的分子变为6，要使分数大小不变，分母应该变为多少．
<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<result>15</result>