A TV set was sold at a 20% discount, which was 720 yuan cheaper than the original price. How much is the original price of this TV set?
一种电视机打八折出售比原价便宜了720元．这种电视机原价是多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">720 / (1/5)</gadget>
<output>3_600</output>

<result>3_600</result>