There is a number, after adding 20% of it, and subtracting 20% of the new number, the result is the original number.
有一个数，增加它的20%后，又减去新数的20%，结果是原数的多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(6/5) * (4/5)</gadget>
<output>24/25 = around 0.96</output>

<result>24/25 = around 0.96</result>