Mom bought 3.5 kilograms of lychees and handed them to the salesperson for 50 yuan, and got back 12.20 yuan. How much is it per kilogram of lychees?
妈妈买了3.5千克的荔枝交给售货员50元，找回12.20元，每千克荔枝多少元？
<gadget id="calculator">50 - 12.2</gadget>
<output>37.8</output>

<gadget id="calculator">37.8 / 3.5</gadget>
<output>10.8</output>

<result>10.8</result>