There are 28 boxes of apples in the fruit store, and a box is sold every day. After 3 days, how many boxes of apples are left in the fruit store?
水果店有28箱苹果，每天卖出a箱，3天后水果店还剩多少箱苹果．
<gadget id="calculator">28 - 3</gadget>
<output>25</output>

<result>25</result>