A wire is 20 meters long, 75% of it is used up, how many meters are left?
一根电线长20米，用去它的75%，还剩多少米．
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">20 * (3/4)</gadget>
<output>15</output>

<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<result>5</result>