What is the ratio of almc005-1.jpg ions to smc005-2.jpg ions in a neutral compound?

The complete question is:
What is the ratio of Al3+ ions to S2- ions in a neutral compound?

Call x the number of atoms of Al(3+) and y the number of atoms of S(2-). The ratio of Al(3+) to S(2-) is x/y

Then, the neutral condition implies  x(3+) + y(2-) = 0

=> 3x = 2y
=> x/y = 2/3

And the ratio is 2/3

2/3