Mom bought 4 kilograms of eggs for 20 yuan, and got back 8 yuan. How much is an egg per kilogram?
妈妈用20元钱买了4千克鸡蛋，找回8元．每千克鸡蛋多少元？
<gadget id="calculator">20 - 8</gadget>
<output>12</output>

<gadget id="calculator">12 / 4</gadget>
<output>3</output>

<result>3</result>