Xiaohua reads a book. He reads (1/6) on the first day and 18 pages on the second day. At this time, the ratio of the number of pages he has read to the number of remaining pages is 1:3. This book has how many pages
小华看一本书，第一天看了(1/6)，第二天看了18页，这时已看的页数与剩下的页数之比是1：3，这本书有多少页？
<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/4) - (1/6)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">18 / (1/12)</gadget>
<output>216</output>

<result>216</result>