If troy has a 3-cm of each brass gold iron lead which cube will have the greatest mass

The cube of gold will have the greatest mass.

Explanation:

All the cubes have the same size, so they have the same volume.

The property that varies among the cubes is density.

D = m/V Multiply both sides by V and transpose.

m = DV

Since V is a constant, m ∝ D.

That is, the cube with the greatest density will have the greatest mass.

The observed densities are

Iron = 7.9 g/cm³

Brass = 8.5 g/cm³

Lead = 11.4 g/cm³

Gold = 19.3 g/cm³

Gold has the greatest density, so the cube of gold has the greatest mass.