In a cuboid, the sum of the three edges starting from a vertex is 7.5 decimeters, what is the sum of the lengths of the edges of this cuboid.
在一个长方体中，从一个顶点出发的三条棱的和是7.5分米，这个长方体的棱长总和是多少．
<gadget id="calculator">7.5 * 4</gadget>
<output>30</output>

<result>30</result>