The price of a TV set sold in the store is 20% lower than the original price, which is exactly 640 yuan lower. How much is the original price of this TV?
商店出售的一种电视机比原价降价20%，正好降低了640元．这种电视机原价是多少元？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">640 / (1/5)</gadget>
<output>3_200</output>

<result>3_200</result>