The ratio of the elements of the neutral compound can be computed from the ionic charges that makes up the compound. The element that makes up the compound is aluminium and sulfur. From the ions aluminium is the cation with a charge of 3+ . The aluminium ion is the cations because it loses 3 electrons from the bonding between it and sulfur. The sulfur is the anion as it gains electrons from the cations.
Aluminium has a charge of 3+ and sulfur has a charge of 2- . The atom of element that makes up the neutral compound can be computed when you cross multiply the charges.
