The upper base of a trapezoid is 12 decimeters, the lower base is 16 decimeters, and the height is 9 decimeters. What is the area of this trapezoid in square decimeters?
一个梯形上底12分米，下底16分米，高9分米，这个梯形的面积是多少平方分米？
<gadget id="calculator">12 + 16</gadget>
<output>28</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">28 * (9/2)</gadget>
<output>126</output>

<result>126</result>