Chengxin Bookstore sold a total of 328 copies of "Huanggang Little Champion" in four days, and 55 copies on the fourth day. How many copies were sold on average in the first three days?
诚信书店四天共卖出《黄冈小状元达标卷》328本，第四天卖出55本，前三天平均每天卖出多少本？
<gadget id="calculator">328 - 55</gadget>
<output>273</output>

<gadget id="calculator">273 / 3</gadget>
<output>91</output>

<result>91</result>