When Xiao Ming reads a story book, the number of pages he has read is (2/5) of the total number of pages in the book. After reading 28 pages, the number of pages he has read is exactly (3/4) of the total number of pages in the book. How many pages are there in this book?
小明读一本故事书，已读的页数是全书总页数的(2/5)，再读28页，则已读的页数就正好是全书总页数的(3/4)，这本书共有多少页？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/4) - (2/5)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">28 / (7/20)</gadget>
<output>80</output>

<result>80</result>