The upper base of the trapezoid is 8cm, the lower base and height are both 5cm, what is its area in cm**2.
梯形的上底是8cm，下底和高都是5cm，它的面积是多少cm**2．
<gadget id="calculator">8 + 5</gadget>
<output>13</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">13 * (5/2)</gadget>
<output>65/2 = around 32.5</output>

<result>65/2 = around 32.5</result>