50 baskets of apples are shipped to the store, each basket weighs 18 kilograms. After some of them are sold, there are 280 kilograms left. How many kilograms are sold?
商店里运来50筐苹果，每筐18千克，卖出一部分以后，剩下280千克，卖出多少千克？
<gadget id="calculator">50 * 18</gadget>
<output>900</output>

<gadget id="calculator">900 - 280</gadget>
<output>620</output>

<result>620</result>