The cafeteria originally had 500 kilograms of rice. After eating bag a, each bag is 50 kilograms. How many kilograms of rice are left?
食堂原有500千克大米，吃掉a袋，每袋50千克，还剩多少千克大米．
<gadget id="calculator">500 - 50</gadget>
<output>450</output>

<result>450</result>