Class 21 needs to plant 7 rows of trees, and the number of trees in each row is equal; the tree Tian Tian planted is the third tree from the front and the third tree from the back. How many trees were planted by the whole class?
二1班要植7行树，每行的棵数相等；田甜植的那一棵树，从前面数是第3棵，从后面数也是第3棵，全班共植树多少棵？
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">5 * 7</gadget>
<output>35</output>

<result>35</result>