Xiaoming's family originally had 500 kilograms of rice, and they ate X bags of 20 kilograms each. How many kilograms are left?
小明家原有500千克大米，吃X袋，每袋20千克，还剩多少千克．
<gadget id="calculator">500 - 20</gadget>
<output>480</output>

<result>480</result>