So the surface area of a rectangular prism is 2wh + 2wl + 2hl
l = 2w
h = 6w
w = w
So replacing all terms with w, we have
2w * 6w + 2w * 2w + 2 * 2w* 6w = 12w^2 + 4w^2 + 24 w^2 = 40w^2 = 1000
w ^ 2 = 1000/40 = 25
w = sqrt(25) = 5
l = 2*5 = 10
h = 6*5 = 30
10*30*5 = the volume = 1500 cm^3
If you don't understand anything feel free to ask.