Xiaoqiang read a famous book during the vacation. He read 20 pages on the first day and 15% of the whole book on the second day. The ratio of the number of pages he read to the number of remaining pages is 1:3. How many pages are there?
小强在假期里看一本名著，第一天看了20页，第二天看了全书的15%，这时看了的页数与剩下页数的比是1：3，这本故事书一共有多少页？
<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">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(1/4) - (3/20)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">20 / (1/10)</gadget>
<output>200</output>

<result>200</result>