Xiaohong reads a story book. She reads 72% of the whole book on the first day and 13% of the whole book on the second day. There are 75 pages left. How many pages are there in the whole book?
小红读一本故事书，第一天读了全书的72%，第二天读了全书的13%，还剩下了75页，全书共有多少页？
<gadget id="calculator">72 / 100</gadget>
<output>18/25 = around 0.72</output>

<gadget id="calculator">13 / 100</gadget>
<output>13/100 = around 0.13</output>

<gadget id="calculator">1 - (18/25) - (13/100)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">75 / (3/20)</gadget>
<output>500</output>

<result>500</result>