The area of a trapezoid is 216 square decimeters, its upper base is 12 decimeters, and its height is 16 decimeters. How many decimeters is the bottom of this trapezoid?
一个梯形的面积是216平方分米，它的上底是12分米，它的高是16分米．这个梯形的下底是多少分米？
<gadget id="calculator">2 / 16</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">216 * (1/8)</gadget>
<output>27</output>

<gadget id="calculator">27 - 12</gadget>
<output>15</output>

<result>15</result>