The volume of the resulting shape, is the area of the cube - 8*the area of each pyramid. (8 corners).
The volume of the cube, is 6*6*6=216.
We see that each pyramid is made out of 3 right isoceles triangles, and one equaliteral. We see that each right isoceles triangle has a leg length of 3, because 2 leg lengths make 6.
To find the volume of each pyramid, we use the formula, \(Volume = \frac{1}{3}base*height\), but we should choose carefully what we want our base and height to be. If we let the equilateral triangle be our base, and the distance from that triangle to the corner be our height, that is some really hard calculations. Instead, we see that each pyramid corner that is cut off is made from 3 right isosceles sides, with one equilateral triangle triangle. If we let an right isoceles triangle be our base, we get much easier calculations.
The area of the base is. \(\frac{3*3}{2}=\frac{9}{2}\), and using the volume formula, each pyramid has an area of \(\frac{1}{3}*\frac{9}{2}*3=\frac{9}{2}\). So the area of the resulting polyhedron is \(216-\frac{9}{2}*8=180\).