A book has 180 pages, Xiaoxiao has already read 40 pages, and the rest should be read within a week. How many pages do you read on average per day?
一本书180页，笑笑已经看了40页，剩下的要在一周内看完．平均每天看多少页？
<gadget id="calculator">180 - 40</gadget>
<output>140</output>

<gadget id="calculator">140 / 7</gadget>
<output>20</output>

<result>20</result>