The formula to find the volume is V = LHW, so here we got the thickness instead of the Weight, it's the same ig
So \(V = 10*6*4 = 240 cm^3\)
The formula to find the density is \(d = \frac{Mass}{Volume}\)
So \(d = \frac{180}{240} = 0.75\) (Always remember that Density have no unity)
Hope this Helps :D