There are 2100 kg of fruit in the fruit shop, and 90 baskets of 20 kg each have been sold. How many kilograms of fruit are left unsold?
果品店里有水果2100千克，已卖出90筐，每筐20千克．还剩下多少千克水果没卖？
<gadget id="calculator">20 * 90</gadget>
<output>1_800</output>

<gadget id="calculator">2_100 - 1_800</gadget>
<output>300</output>

<result>300</result>