To plant 8,400 trees, 600 were planted in the first three days, so how many days will it take to plant the rest?
要栽8400棵树，前三天栽600棵，照这样计算剩下的还要几天栽完？
<gadget id="calculator">8_400 - 600</gadget>
<output>7_800</output>

<gadget id="calculator">600 / 3</gadget>
<output>200</output>

<gadget id="calculator">7_800 / 200</gadget>
<output>39</output>

<result>39</result>