A piece of cloth is (2/3) meters long, first use up (1/2), and then use up (1/3). What fraction of it is left?
一块布长(2/3)米，先用去它的(1/2)，又用去它的(1/3)．还剩下它的几分之几？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/2) - (1/3)</gadget>
<output>1/6 = around 0.166667</output>

<result>1/6 = around 0.166667</result>