Xiao Ming reads a book, reads 20% of the whole book on the first day, and reads 15 pages less on the second day than on the first day. There are 75 pages left to read. How many pages does this book have?
小明读一本书，第一天读了全书的20%，第二天比第一天少读15页．还剩75页没读．这本书有多少页？
<gadget id="calculator">75 - 15</gadget>
<output>60</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) * 2</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">60 / (3/5)</gadget>
<output>100</output>

<result>100</result>