The bookstore sells books at a 25% discount. Xiao Ming spent 15 yuan on the book. How much did Xiao Ming save?
书店打七五折销售图书，小明买书花了15元钱，小明节省了多少钱？
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">15 / (3/4)</gadget>
<output>20</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>