The perimeter of a right-angled trapezoid is 55 decimeters, and the two sides are 12 decimeters and 15 decimeters respectively. What is the area of this rectangle in square feet?
一个直角梯形的周长是55分米，两条腰分别长12分米和15分米．这个直角梯形的面积是多少平方分米．
<gadget id="calculator">55 - 12 - 15</gadget>
<output>28</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">28 * 6</gadget>
<output>168</output>

<result>168</result>