The area of a trapezoid is 90 decimeters square, the upper base is 5 decimeters, and the lower base is 10 decimeters. What is its height?
一个梯形的面积是90平方分米，上底是5分米，下底是10分米，它的高是多少分米．
<gadget id="calculator">5 + 10</gadget>
<output>15</output>

<gadget id="calculator">2 / 15</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">90 * (2/15)</gadget>
<output>12</output>

<result>12</result>