There are 15 cypress trees in the campus. The willow trees are cypress trees (2/3) and pine trees (2/7). How many pine trees are there?
校园里有柏树15棵，柳树的棵树是柏树的(2/3)，又是松树的(2/7)，松树有几棵？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

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

<gadget id="calculator">(2/3) / (2/7)</gadget>
<output>7/3 = around 2.333333</output>

<gadget id="calculator">15 * (7/3)</gadget>
<output>35</output>

<result>35</result>