Daxin Mall sold 850 washing machines in October, and sold less (1/5) in September than in October. How many washing machines were sold in September?
大新商场十月份卖出洗衣机850台，九月份比十月份少卖(1/5)，九月份卖出多少台洗衣机？
<gadget id="calculator">1 / 5</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">850 * (4/5)</gadget>
<output>680</output>

<result>680</result>