For a book, read 30% of the total pages of the book on the first day, read 20% of the total pages of the book on the second day, read 18 pages on the second day, how many pages did you read on the first day?
一本书，第一天看了这本书总页数的30%，第二天看了这本书总页数的20%，第二天看了18页，第一天看了多少页？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">18 / (1/5)</gadget>
<output>90</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">90 * (3/10)</gadget>
<output>27</output>

<result>27</result>