The store sells 75 boxes of apples on the first day, and 70 boxes of apples on the second day. The first day sells 400 more than the second day. How much is the average apple per box?
商店第一天卖出75箱苹果，第二天卖出70箱苹果，第一天比第二天多卖了400元，平均每箱苹果多少元？
<gadget id="calculator">75 - 70</gadget>
<output>5</output>

<gadget id="calculator">400 / 5</gadget>
<output>80</output>

<result>80</result>