book has 150 pages in total, Xiaogang has already read 90 pages, and the rest will be finished within 3 days. How many pages do you read on average every day?
一本书共有150页，小刚已经看了90页，剩下的要在3天内看完，平均每天看多少页？
<gadget id="calculator">150 - 90</gadget>
<output>60</output>

<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<result>20</result>