When Xiaohong reads a book, the ratio of the number of pages she has read to the number of pages she has not read is 1:3. If you read another 30 pages, the ratio of the number of pages you have read to the number of pages you have not read is 1:2. How many pages does this book have?
小红读一本书，已读的和末读的页数比是1：3．如果再读30页，则已读的和末读的页数之比为1：2．这本书共有多少页？
<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<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">(1/3) - (1/4)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">30 / (1/12)</gadget>
<output>360</output>

<result>360</result>