It is known that the upper base of the trapezoid is a centimeter, the height is 5 cm, and the area is x square centimeters, then how long is its lower base in centimeters?
已知梯形的上底是a厘米，高是5厘米，面积是x平方厘米，那么它的下底长多少厘米．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>