Naughty bought 6 kilograms of apples, handed them to the salesperson for 30 yuan, and got back 4.80 yuan. How much is a kilogram of apples? (solution by equation)
淘气买了6千克的苹果，交给售货员30元，找回4.80元，每千克苹果多少钱？(用方程解)
<gadget id="calculator">30 - 4.8</gadget>
<output>25.2</output>

<gadget id="calculator">25.2 / 6</gadget>
<output>4.2</output>

<result>4.2</result>