The area of the trapezoid is 18 square decimeters, the sum of the upper and lower bases is 9 decimeters, what is the height in decimeters.
梯形的面积是18平方分米，上下底边的和是9分米，高是多少分米．
<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">18 * (2/9)</gadget>
<output>4</output>

<result>4</result>