Subtract 8 from the numerator of (12/18), how much should be subtracted from the denominator to keep the size of the fraction unchanged.
把(12/18)的分子减去8，要使分数的大小不变，分母应减去多少．
<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<gadget id="calculator">12 / 4</gadget>
<output>3</output>

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

<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<result>12</result>