Xiao Ming reads a book. He reads 12 pages on the first day, and the rest (1/4) on the second day. At this time, the number of pages he has read and the number of pages he has not read are exactly equal. How many pages are there in this book?
小明读一本书，第一天读了12页，第二天读了剩下的(1/4)，这时读过的和没读的页数正好相等，这本书共有多少页？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">12 * (1/4)</gadget>
<output>3</output>

<gadget id="calculator">12 - 3</gadget>
<output>9</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) - (1/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">9 / (1/4)</gadget>
<output>36</output>

<result>36</result>