The area of a trapezoid is 80㎡, the height is 8m, the upper base is 4.5m, what is the lower base?
一个梯形的面积是80㎡，高是8m，上底是4.5m，下底是多少．
<gadget id="calculator">2 / 8</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">80 * (1/4)</gadget>
<output>20</output>

<gadget id="calculator">20 - 4.5</gadget>
<output>15.5</output>

<result>15.5</result>