The sum of the upper and lower bases of a trapezoid is 26 decimeters, and the height is 12 decimeters. What is its area in square decimeters?
一个梯形的上、下底之和是26分米，高是12分米，它的面积是多少平方分米．
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">26 * 6</gadget>
<output>156</output>

<result>156</result>