Students plant trees. The fifth grade planted 30 trees, which was less than the sixth grade (2/7). How many trees were planted in the sixth grade?
同学们植树．五年级植树30棵，比六年级的棵数少(2/7)，六年级植树多少棵？
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (2/7)</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">30 / (5/7)</gadget>
<output>42</output>

<result>42</result>