Add 10 to the numerator of (2/3), how much should be added to the denominator to keep the size of the fraction unchanged.
(2/3)的分子加上10，要使分数的大小不变，分母应该加上多少．
<gadget id="calculator">2 + 10</gadget>
<output>12</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

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

<gadget id="calculator">18 - 3</gadget>
<output>15</output>

<result>15</result>