The area of a trapezoid is 60 square decimeters. It is known that the upper base is 12 decimeters and the lower base is 18 decimeters. What is its height?
一个梯形的面积是60平方分米，已知上底是12分米，下底是18分米，它的高是多少分米．
<gadget id="calculator">12 + 18</gadget>
<output>30</output>

<gadget id="calculator">2 / 30</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">60 * (1/15)</gadget>
<output>4</output>

<result>4</result>