Wang Meng bought a backgammon point reader, the original price was 840 yuan, and now it is on sale at a 20% discount. How much did Wang Meng actually spend?
王蒙买了一个步步高点读机，原价840元，现在打八折出售，王蒙实际花了多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">840 * (4/5)</gadget>
<output>672</output>

<result>672</result>