The area of a right-angled trapezoid with a height of 4 decimeters is 68 decimeters squared. If the upper base is increased by 6 decimeters, it becomes a rectangle. Then how many decimeters is the lower base of the trapezoid.
一个高是4分米的直角梯形的面积是68平方分米，如果上底增加6分米，它就成了一个长方形，那么这个梯形的下底是多少分米．
<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">68 * (1/2)</gadget>
<output>34</output>

<gadget id="calculator">34 + 6</gadget>
<output>40</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<result>20</result>