A copy of "Children's Stories" is originally priced at 20 yuan, and now it is on sale at a 25% discount. How much cheaper can it be?
一本《儿童故事》原价20元，现在打七五折出售，可以便宜多少元？
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 * (1/4)</gadget>
<output>5</output>

<result>5</result>