There are 15 pine trees in the school. The number of cypress trees is pine (2/5) and willow (1/3). How many willows are there?
学校有松树15棵，柏树的棵数是松树的(2/5)，同时又是柳树的(1/3)，柳树有多少棵？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(2/5) / (1/3)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">15 * (6/5)</gadget>
<output>18</output>

<result>18</result>