A rope is 8 meters long, (1/2) is used up, and (1/2) meter is used up, how much is left.
一根绳子长8米，用去(1/2)，又用去(1/2)米，还剩多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">8 * (1/2)</gadget>
<output>4</output>

<gadget id="calculator">8 - 4 - (1/2)</gadget>
<output>7/2 = around 3.5</output>

<result>7/2 = around 3.5</result>