The sum of the upper and lower bases of a trapezoid is 12 decimeters, which is three times as high. What is the area of the trapezoid in square decimeters?
一个梯形上下底的和是12分米，是高得3倍，这个梯形的面积是多少平方分米．
<gadget id="calculator">12 / 3</gadget>
<output>4</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<result>24</result>