There is a 12-meter-long rope used for the first time (1/4), how many meters are left?
有一根12米长的绳子第一次用去它的(1/4)，还剩多少米．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">12 * (3/4)</gadget>
<output>9</output>

<result>9</result>