Xiao Ming reads a book, and after reading 40%, there are 54 pages left. How many pages are there in this book?
小明看一本书，看了40%后，还剩下54页，这本书共有多少页？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">54 / (3/5)</gadget>
<output>90</output>

<result>90</result>