The sixth grade students planted pine trees, and Class 1 and Class 2 planted a total of 658 trees. There are 42 people in the first class, and each person plants 9 trees on average, and there are 40 people in the second class, how many trees are planted by each person on average?
六年级同学种松树，一班和二班共种658棵．一班有42人，平均每人种9棵，二班有40人，平均每人种多少棵？
<gadget id="calculator">9 * 42</gadget>
<output>378</output>

<gadget id="calculator">658 - 378</gadget>
<output>280</output>

<gadget id="calculator">280 / 40</gadget>
<output>7</output>

<result>7</result>