Increase the numerator of (3/5) by 12, what is the denominator, and the size of the fraction remains the same.
把(3/5)的分子增加12，分母要多少，分数的大小不变．
<gadget id="calculator">3 + 12</gadget>
<output>15</output>

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

<gadget id="calculator">5 * 5</gadget>
<output>25</output>

<gadget id="calculator">25 - 5</gadget>
<output>20</output>

<result>20</result>