A mathematics teaching paper by Mr. Zhang received a manuscript fee of 500 yuan. According to regulations should pay 20% personal income tax. How much did Mr. Zhang actually get for the manuscript fee?
张老师的一篇数学教学论文，得到了500元的稿费．按规定应缴纳20%的个人所得税．张老师实际得到稿费多少元．
<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">500 * (4/5)</gadget>
<output>400</output>

<result>400</result>