Students from three classes in grade six planted trees. The first class planted 39 trees, and the number of trees planted by the second class was 2/3 of that of the first class. The second class planted 6 trees twice as many as the third class. How many trees did the third class plant?
六年级三个班同学植树．一班植树39棵，二班栽的棵数是一班的(2/3)，二班比三班的2倍少6棵，三班栽了多少棵？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">39 * (2/3)</gadget>
<output>26</output>

<gadget id="calculator">26 + 6</gadget>
<output>32</output>

<gadget id="calculator">32 / 2</gadget>
<output>16</output>

<result>16</result>