A trapezoid has an upper base of 5 cm, a lower base of 10 cm, and a height of 8 cm. What is its area in cm**2.
有一个梯形的上底是5cm，下底是10cm，高是8cm．它的面积是多少cm**2．
<gadget id="calculator">5 + 10</gadget>
<output>15</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<result>60</result>