There are three classes in grade six planting trees. The assignment is as follows: Class A will plant 40% of the total number of trees planted by three classes. The ratio of trees planted by classes B and C is 3:4. When Class A plants 100 trees, Just completed the three classes of tree planting (2/7) of the total number of trees. How many trees are planted in Class C?
六年级三个班植树，任务分配是：甲班要植三个班植树总棵树的40%，乙、丙两班植树的棵树的比是3：4，当甲班植树100棵时，正好完成三个班植树总棵树的(2/7)．丙班植树多少棵？
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">100 / (2/7)</gadget>
<output>350</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">350 * (3/5) * (4/7)</gadget>
<output>120</output>

<result>120</result>