Mom spent 20 yuan to buy 2.5 kilograms of apples, and there is 10.5 yuan left, how much is the apple per kilogram?
妈妈用了20元买了2.5千克的苹果，还剩下10.5元，则每千克苹果多少元？
<gadget id="calculator">20 - 10.5</gadget>
<output>9.5</output>

<gadget id="calculator">9.5 / 2.5</gadget>
<output>3.8</output>

<result>3.8</result>