Xiao Ming reads a book, and the number of pages he has read is the number of unread pages (3/2). He reads another 30 pages. At this time, the number of pages he has read is the number of unread pages (7/3). How many pages does the book have?
小明读一本书，已读的页数是未读页数的(3/2)，他再读30页，这时已读的页数是未读页数的(7/3)，这本书共多少页？
<gadget id="calculator">3 + 7</gadget>
<output>10</output>

<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(7/10) - (3/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">30 / (1/10)</gadget>
<output>300</output>

<result>300</result>