If a jacket with a price tag of 800 yuan is sold at a 20% discount, it can still make a profit of 40 yuan. What is the cost price of the jacket?
一件标价800元的上衣，若按8折销售仍可获利40元，则这件上衣的成本价是多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">800 * (4/5)</gadget>
<output>640</output>

<gadget id="calculator">640 - 40</gadget>
<output>600</output>

<result>600</result>