Tickets for the amusement park used to be 50 yuan each, and there was a 20% discount during the "June 1st" period. How much can you save by buying a ticket?
游乐场的门票原来每张50元，"六一"期间八折优惠，购买一张门票能省多少元．
<gadget id="calculator">50 * 0.8</gadget>
<output>40</output>

<gadget id="calculator">50 - 40</gadget>
<output>10</output>

<result>10</result>