Xiao Ding wants to read a 420-page storybook, but he has already read 270 pages, and the rest will be finished in 3 days. How many pages do he read on average every day?
小丁要看420页的故事书，已经看了270页，剩下的要在3天看完，平均每天看多少页？
<gadget id="calculator">420 - 270</gadget>
<output>150</output>

<gadget id="calculator">150 / 3</gadget>
<output>50</output>

<result>50</result>