Xiao Ming reads a 118-page book, 15 pages on the first day, 4 more pages on the second day, and the rest in four days. How many pages are read on average per day?
小明读一本118页的书，第一天读15页，第二天多读4页，剩下的分四天读完，平均每天读多少页．
<gadget id="calculator">118 - 15 - 15 - 4</gadget>
<output>84</output>

<gadget id="calculator">84 / 4</gadget>
<output>21</output>

<result>21</result>