The mean is all of them added together divided by the number, so multiple the mean by the number of sides, 3, and that's the perimeter. 18 x 3 = 54
If you meant to solve for x...
Density is <u>mass</u>
volume
With those dimensions, the volume of the pyramid is;
V = lw(h/3)
V = (5)(6)(8/3)
V = 80 cm^3
D = <u> 40 g </u> = 1 g/cm^3
80 cm^3
I believe it would be 12.16
