On Children's Day, Xinhua Bookstore held promotional activities, and all books were sold at 15% off the original price. Xiao Ming bought a set of books with a price tag of 150 yuan. How much is it cheaper than the original price after the discount?
"六一"儿童节那天，新华书店举行促销活动，所有图书按原价的八五折出售．小明买了一套标价150元的图书，打折后比原价便宜多少元？
<gadget id="calculator">85 / 100</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">150 * (17/20)</gadget>
<output>255/2 = around 127.5</output>

<gadget id="calculator">150 - (255/2)</gadget>
<output>45/2 = around 22.5</output>

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