Here's how to determine it:

* Tin(II) indicates that tin has a +2 oxidation state (Sn²⁺).

* Sulfite refers to the sulfite ion, which has a -2 charge (SO₃²⁻).

To balance the charges, we need one tin(II) ion (Sn²⁺) and one sulfite ion (SO₃²⁻). This gives us the formula SnSO₃.