rope is 3 meters long, (1/3) is used up, how many meters are left?
一根绳子长3米，用去了(1/3)，还剩下多少米．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">3 * (2/3)</gadget>
<output>2</output>

<result>2</result>