A book has 200 pages, and 40 pages have been read, how many pages have been read compared to unread pages?
一本书有200页，已经读了40页，已读的比没读的少多少页？
<gadget id="calculator">200 - 40</gadget>
<output>160</output>

<gadget id="calculator">160 - 40</gadget>
<output>120</output>

<result>120</result>