A right-angled trapezoid, the upper base is 10 decimeters, and the lower base is 12 decimeters. If a square is cut from this trapezoid, what is left is exactly a triangle. What is the area of this triangle?
一个直角梯形，上底是10分米，下底是12分米，如果从这个梯形中剪去一个正方形，剩下的正好是一个三角形，这个三角形的面积是多少平方分米．
<gadget id="calculator">12 - 10</gadget>
<output>2</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">2 * 5</gadget>
<output>10</output>

<result>10</result>