12:18 subtract 8 from the former term, what should be the latter term in order to keep the ratio unchanged.
12：18的前项减去8，要使比值不变，后项应该多少．
<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>