trapezoid and a triangle have the same area and height, the upper base of the trapezoid is 13dm, the lower base is 17dm, how many decimeters is the base of the triangle.
一个梯形与一个三角形面积相等，高相等，梯形的上底是13dm，下底是17dm，三角形的底是多少分米．
<gadget id="calculator">13 + 17</gadget>
<output>30</output>

<result>30</result>