The sum of the upper and lower bases of a trapezoid is 20 meters and the height is 6 meters. What is its area in square meters?
一个梯形的上下底之和是20米，高是6米，它的面积是多少平方米．
<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">20 * 3</gadget>
<output>60</output>

<result>60</result>