Reading a story book, I read (1/5) of the whole book on the first day, and read 120 pages on the second day. At this time, the ratio of the number of read pages to the number of unread pages is 7:3. How many pages are there in this book? ?
看一本故事书书，第一天看了全书的(1/5)，第二天看了120页，这时已读与未读页数的比是7：3，这本书有多少页？
<gadget id="calculator">7 + 3</gadget>
<output>10</output>

<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(7/10) - (1/5)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">120 / (1/2)</gadget>
<output>240</output>

<result>240</result>