Add 36 to the denominator of (5/12), how much should be added to the numerator to keep the size of the fraction constant?
(5/12)的分母加上36，要使分数的大小不变，分子应加上多少？
<gadget id="calculator">12 + 36</gadget>
<output>48</output>

<gadget id="calculator">48 / 12</gadget>
<output>4</output>

<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<result>15</result>