During the summer vacation, Xiaofang plans to finish reading the book "One Hundred Thousand Whys" in 20 days, reading 15 pages a day. Actually read 20 pages a day, how many days did she actually finish reading it earlier than planned?
暑假期间，小芳计划20天读完《十万个为什么》这本书，每天读15页．实际每天读20页，她实际比计划提前几天读完？
<gadget id="calculator">15 / 20</gadget>
<output>3/4 = around 0.75</output>

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

<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<result>5</result>