The supermarket shipped 90 kilograms of green vegetables, sold 40 kilograms in the morning and 30 kilograms in the afternoon, how many kilograms are left?
超市运来90千克青菜，上午卖出40千克，下午卖出30千克，还剩多少千克？
<gadget id="calculator">90 - 40 - 30</gadget>
<output>20</output>

<result>20</result>