the formula for density is mass divided by volume (m/v). In this problem, you mus first find the volume of the square block. The formula for volume is length multiplied by width multiplied by height (LxWxH). To solve for volume you plug in the values to the equation: 6x4x2 = 48.
Now, you have the volume, and you have the density. Now you need to solve for mass. Plug in the values you have into the density equation (d=m/v):
7=m/48
to isolate M, multiply each side by 48. this leaves you with 7x48 = m. now all thats left is to solve. 7x48 = 336g. You can double check by plugging the values back into the equation. 336/48 = 7.
