Uncle Zhang went to the vegetable market and bought 6.5 kilograms of Chinese cabbage at a vegetable stall. He paid 20 yuan and got back 1.8 yuan. How much is it sold per kilogram of Chinese cabbage?
张大爷去到菜场，在一个菜摊买了6.5千克小白菜，付出20元，找回1.8元，每千克小白菜卖多少元？
<gadget id="calculator">20 - 1.8</gadget>
<output>18.2</output>

<gadget id="calculator">18.2 / 6.5</gadget>
<output>2.8</output>

<result>2.8</result>