The area of a trapezoid is 18 square decimeters, its upper base is 3 decimeters, its height is 4 decimeters, how many decimeters is its lower base?
一个梯形的面积是18平方分米，它的上底是3分米，高是4分米，下底是多少分米？
<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">18 * (1/2)</gadget>
<output>9</output>

<gadget id="calculator">9 - 3</gadget>
<output>6</output>

<result>6</result>