The sum of the upper and lower bases of the trapezoid is 20 meters, and the height is 7 meters. What is the area of the trapezoid in square meters?
梯形上下底的和是20米，高是7米，梯形的面积是多少平方米．
<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">20 * (7/2)</gadget>
<output>70</output>

<result>70</result>