A piece of rope, use up (2/3) first, then use up the rest (1/3), how much is left in the end
一段绳子，先用去(2/3)，再用去剩下的(1/3)，最后还剩多少
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<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">(1/3) * (2/3)</gadget>
<output>2/9 = around 0.222222</output>

<result>2/9 = around 0.222222</result>