Here's how it's determined:

* Aluminum (Al): Aluminum is a metal with a +3 charge.

* Ethanoate (CH₃COO⁻): This is the anion (negatively charged ion) derived from ethanoic acid (acetic acid). It has a -1 charge.

To balance the charges, we need three ethanoate ions for every one aluminum ion:

* Al³⁺ + 3 CH₃COO⁻ → Al(CH₃COO)₃