There are 20 willows in the campus, the poplars are from willows (7/10), and the pagoda trees are from poplars (5/7). How many locust trees are there?
校园里有柳树20棵，杨树是柳树的(7/10)，槐树是杨树的(5/7)．槐树有多少棵？
<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">20 * (7/10) * (5/7)</gadget>
<output>10</output>

<result>10</result>