(Only the calculation formula is not included) The original 420 units of air conditioners in Xinglong Electric City were sold (1/5) in the first week, and 25% were sold in the second week. How many units are left unsold?
(只列算式不计算)兴隆电器城原有空调420台，第一周售出(1/5)，第二周售出25%，还剩下多少台没有售出？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/5) + (1/4)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (9/20)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">420 * (11/20)</gadget>
<output>231</output>

<result>231</result>