Remove 8 from the numerator of (16/18), and reduce the denominator to keep the fraction value unchanged.
把(16/18)的分子去掉8，要使分数值不变，分母就减少多少．
<gadget id="calculator">16 - 8</gadget>
<output>8</output>

<gadget id="calculator">16 / 8</gadget>
<output>2</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">18 - 9</gadget>
<output>9</output>

<result>9</result>