The number of poplar trees in the campus is 2/3 of that of pine trees, and the number of willow trees is 2/5 of that of pine trees. There are 20 known poplars, how many willows are there?
校园里杨树的棵数是松树的(2/3)，柳树的棵数是松树的(2/5)．已知杨树的有20棵，柳树有多少棵？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">20 / (2/3)</gadget>
<output>30</output>

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

<gadget id="calculator">30 * (2/5)</gadget>
<output>12</output>

<result>12</result>