A piece of wood is 12 meters long, if (1/4) of it is used up, how many meters are left?
一根木材长12米，用去其中的(1/4)，还剩多少米．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">12 * (1/4)</gadget>
<output>3</output>

<gadget id="calculator">12 - 3</gadget>
<output>9</output>

<result>9</result>