Aunt Li bought 3.5 kilograms of oranges and paid 50 yuan, and the salesperson got back 22.7 yuan. How much is the price per kilogram of oranges?
李阿姨买3.5千克橘子，付出50元，营业员找回22.7元．每千克橘子的售价是多少元？
<gadget id="calculator">50 - 22.7</gadget>
<output>27.3</output>

<gadget id="calculator">27.3 / 3.5</gadget>
<output>7.8</output>

<result>7.8</result>