Tickets for Strange Slope Park are usually 40 yuan each, and there is a 20% discount during the National Day. How much yuan can you save by buying a ticket.
怪坡园门票平常每张40元，国庆节期间八折优惠，购买一张门票可省多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">40 * (4/5)</gadget>
<output>32</output>

<gadget id="calculator">40 - 32</gadget>
<output>8</output>

<result>8</result>