There is a trapezoidal lawn with an upper base of 12 meters, a lower ground of 18 meters, and a height of 10 meters. What is the area of this lawn in square meters?
有一块梯形状的草坪，上底12米，下地18米，高10米，这块草坪的面积是多少平方米？
<gadget id="calculator">12 + 18</gadget>
<output>30</output>

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

<gadget id="calculator">30 * 5</gadget>
<output>150</output>

<result>150</result>