A wire is 20 meters long, if (1/2) of it is used up, how many meters are left?
一根电线长20米，用去它的(1/2)，还剩多少米．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">20 * (1/2)</gadget>
<output>10</output>

<result>10</result>