Xiaohua's mother went to the fruit store and bought 3 kilograms of bananas and 3 kilograms of apples. The total cost was 25.5 yuan, and the bananas were 4.5 yuan per kilogram. How much is an apple per kilogram?
小华妈妈到水果商店买了香蕉和苹果各3千克，共花了25.5元，香蕉每千克4.5元．苹果每千克多少元？
<gadget id="calculator">25.5 / 3</gadget>
<output>8.5</output>

<gadget id="calculator">8.5 - 4.5</gadget>
<output>4</output>

<result>4</result>