Use two identical trapezoids to form a parallelogram with an area of 36 square decimeters. It is known that the sum of the upper and lower bases of each trapezoid is 12 decimeters, what is the height of the trapezoid in decimeters.
用两个完全一样的梯形拼成一个面积是36平方分米的平行四边形．已知每个梯形的上底和下底的和是12分米，梯形的高是多少分米．
<gadget id="calculator">36 / 12</gadget>
<output>3</output>

<result>3</result>