If the upper base of a trapezoid is extended by 2 meters, the area increases by 4 square meters, and the original trapezoid becomes a rectangle with a length of 6 meters. Find the area of the original trapezoid in square meters?
一个梯形的上底延长2米，则面积增加4平方米，并且原梯形变成一个长6米的长方形，求原来梯形面积是多少平方米？
<gadget id="calculator">6 - 2</gadget>
<output>4</output>

<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<gadget id="calculator">2 / 2 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">10 * 4 * (1/2)</gadget>
<output>20</output>

<result>20</result>