Students in Class 4 and Class 2 have to make 840 flowers, and they have already made 300 flowers, and the rest need to be completed by 12 groups. On average, how many flowers does each group need to make?
四2班同学要做840朵花，已经做了300朵，剩下的要12个小组完成．平均每个小组还要做多少朵？
<gadget id="calculator">840 - 300</gadget>
<output>540</output>

<gadget id="calculator">540 / 12</gadget>
<output>45</output>

<result>45</result>