Xiao Ming wants to read a 315-page storybook. He has been reading it for 4 days and there are 115 pages left. How many pages does Xiao Ming read on average every day?
小明要读315页的故事书，已经读了4天，还剩115页没有读，小明平均每天读多少页？
<gadget id="calculator">315 - 115</gadget>
<output>200</output>

<gadget id="calculator">200 / 4</gadget>
<output>50</output>

<result>50</result>