The upper base of a trapezoid is 5 decimeters, the lower base is 7 decimeters, and the height is 80 centimeters. What is its area?
一个梯形的上底是5分米，下底是7分米，高是80厘米，它的面积是多少．
<gadget id="calculator">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">80 / 10</gadget>
<output>8</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">12 * 4</gadget>
<output>48</output>

<result>48</result>