Xiaohong reads a story book. On the first day, she reads 1/7 of the whole book, and on the second day, she reads 12 pages. At this time, the ratio of the number of pages she has read to the number of pages she has not read is 1:3. How many pages does this storybook have? (Click on the idea: After reading it the next day, the number of pages I have read is (1/(1+3))=(1/4) of the whole book).
小红看一本故事书，第一天看了全书的(1/7)，第二天又看了12页，这时已看页数与未看页数的比是1：3．这本故事书共有多少页？(思路点击：第二天看后，已看页数是全书的(1/(1+3))=(1/4))．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/4) - (1/7)</gadget>
<output>3/28 = around 0.107143</output>

<gadget id="calculator">12 / (3/28)</gadget>
<output>112</output>

<result>112</result>