The volume of a prism is given by
Where is the base are and is the height.
So, if two prisms have the same height and the same volume, they must have the same base area.
The first base is an equilateral triangle, which means that the height is given by
So, the area is
The area of the second base is simply the product of the dimensions, so it is
Since the two areas must be the same, we have