Li Ming reads a book. Originally, he planned to read 20 pages a day and finished it in 18 days. Now he reads 4 more pages a day. How many days does it take to finish the book? (Use proportion knowledge to answer.)
李明读一本书，原来准备每天读20页，18天读完，现在每天多读4页，读完这本书现在用多少天？(用比例知识解答．)
<gadget id="calculator">20 * 18</gadget>
<output>360</output>

<gadget id="calculator">20 + 4</gadget>
<output>24</output>

<gadget id="calculator">360 / 24</gadget>
<output>15</output>

<result>15</result>