Wang Qiang reads a story book and has read 80 pages. The ratio of the number of pages read to the number of unread pages is 4:5. How many pages does this storybook have?
王强读一本故事书，已经读了80页，已读页数和未读页数的比是4：5．这本故事书有多少页？
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">80 / (4/9)</gadget>
<output>180</output>

<result>180</result>