If 9 is subtracted from the numerator of (12/16), how much should the denominator be subtracted to keep the size of the fraction unchanged.
如果把(12/16)的分子减去9，要使分数的大小不变，分母应减去多少．
<gadget id="calculator">12 / 3</gadget>
<output>4</output>

<gadget id="calculator">16 / 4</gadget>
<output>4</output>

<gadget id="calculator">16 - 4</gadget>
<output>12</output>

<result>12</result>