For a trapezoid, the product of the upper base and the height is 48, and the product of the lower base and the height is 84. What is the area of the trapezoid?
一个梯形，上底与高的积是48，下底与高的积是84，这个梯形的面积是多少．
<gadget id="calculator">48 + 84</gadget>
<output>132</output>

<gadget id="calculator">132 / 2</gadget>
<output>66</output>

<result>66</result>