Xiaomei reads a book, and after reading 40 pages of the whole book, there are still (5/9) of the total number left. How many pages are there in the whole book?
小梅看一本书，看了全书的40页，还剩下总数的(5/9)，全书共有多少页？
<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">1 - (5/9)</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">40 / (4/9)</gadget>
<output>90</output>

<result>90</result>