There are 15 locust trees in the school, the poplar tree is locust tree (2/3), and the willow tree (2/7). How many willow trees are there?
学校有槐树15棵，杨树的棵树是槐树的(2/3)，又是柳树的(2/7)．柳树有多少棵？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">15 * (2/3)</gadget>
<output>10</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">10 / (2/7)</gadget>
<output>35</output>

<result>35</result>