There is a popular science book, the original price is 150 yuan per set, and now it is sold at a 15% discount. How much cheaper is a set?
有一种科普书，原价每套150元，现按八五折出售，一套可便宜多少元？
<gadget id="calculator">85 / 100</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">1 - (17/20)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">150 * (3/20)</gadget>
<output>45/2 = around 22.5</output>

<result>45/2 = around 22.5</result>