A rectangle with a length of 15 cm is extended by 4 cm to form a trapezoid with an area increased by 12 cm2. What is the area of the trapezoid in square centimeters?
将一个长15厘米的长方形的一条长边延长4厘米后，变成了一个梯形，面积增加了12平方厘米．求梯形的面积是多少平方厘米？
<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">12 * (1/2)</gadget>
<output>6</output>

<gadget id="calculator">6 * 15</gadget>
<output>90</output>

<gadget id="calculator">90 + 12</gadget>
<output>102</output>

<result>102</result>