A number is 90, what is it after reducing it by 20%.
一个数是90，减少它的20%后是多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">90 * (4/5)</gadget>
<output>72</output>

<result>72</result>