Mom spent 37 yuan to buy 4 kilograms of sweet oranges and 3 kilograms of apples. It is known that sweet oranges are 5.2 yuan per kilogram. How much is an apple per kilogram?
妈妈花了37元钱买了4千克甜橙和3千克苹果，已知甜橙每千克5.2元，苹果每千克多少钱？
<gadget id="calculator">5.2 * 4</gadget>
<output>20.8</output>

<gadget id="calculator">37 - 20.8</gadget>
<output>16.2</output>

<gadget id="calculator">16.2 / 3</gadget>
<output>5.4</output>

<result>5.4</result>