A wire is 12 meters long, 30% of it is used up, and 50% of it is used up, how many meters are left?
一根铁丝长12米，用去它的30%，再用去它的50%，还剩多少米．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (3/10) - (1/2)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">12 * (1/5)</gadget>
<output>12/5 = around 2.4</output>

<result>12/5 = around 2.4</result>