A student is using colored beads to make a model of aluminum sulfate, Al2(SO4)3. Aluminum atoms are represented by green beads, sulfur atoms by blue beads, and
oxygen atoms by yellow beads. What combination of beads should the student use for
the model?

The combination of beads should the student use for  the model :2 green, 3 blue and 12 yellow

In the chemical formula of a compound there are numbers:

1. The number indicates the number of atoms written after the element symbol

2. The number after the parentheses represents the number multiplied by the number of atoms in parentheses.

3. The number before the chemical formula shows the number of molecules behind it, which is usually used in equations

To calculate the beads needed to make a model, we must count the number of atoms of the Al₂(SO₄)₃ molecule

In the Al₂ (SO₄) ₃ molecule there are 3 atoms : Al, S, and O

So the combination of beads

2 green(for Al), 3 blue(for S) and 12 yellow(for O)

im not exactly sure but i think its b!