Read a storybook, read 90 pages in the first week, and read 40% of the whole book in the second week, this is the ratio of the number of pages read to the number of unread pages is 7:3, how many pages are there in this storybook ．
读一本故事书，第一周读了90页，第二周读了全书的40%，这是已读的页数与未读的页数比是7：3，这本故事书共有多少页．
<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">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(7/10) - (2/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">90 / (3/10)</gadget>
<output>300</output>

<result>300</result>