The young pioneers participated in the tree planting activities, and each person planted the same number of trees. The first team has 15 people, and the second team has 9 people. The first team planted 42 more trees than the second team. How many trees are planted per person on average?
少先队员参加植树活动，每人植树的棵数同样多．第一小队15人，第二小队9人，第一小队比第二小队多植树42棵．平均每人植树多少棵？
<gadget id="calculator">15 - 9</gadget>
<output>6</output>

<gadget id="calculator">42 / 6</gadget>
<output>7</output>

<result>7</result>