In order to protect the earth, some students in the fourth grade participated in the tree planting activity. There were 28 students in the first class, and a total of 308 trees were planted. There were 39 students in the second class, and a total of 351 trees were planted. How many fewer trees were planted per person in the second class than in the first class?
为了保护地球，四年级部分同学参加了植树活动，一班28人，共植树308棵，二班39人，共植树351棵，二班比一班平均每人少植树多少棵？
<gadget id="calculator">308 / 28</gadget>
<output>11</output>

<gadget id="calculator">351 / 39</gadget>
<output>9</output>

<gadget id="calculator">11 - 9</gadget>
<output>2</output>

<result>2</result>