Add 6 to the denominator of (5/6), how much should be added to the numerator to keep the size of the fraction unchanged.
把(5/6)的分母加上6，要使分数大小不变，分子应加上多少．
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 - 5</gadget>
<output>5</output>

<result>5</result>