Answer:
+2
Step-by-step explanation:
Oxygen ions always have the charge of -2. Since Fe is in the transition metal stage, it doesn't have a specific set of ions unless specifically shown. In the equation FeO, we would have to have a +2 charge when equalling the two atoms together. So when combines the charges would look like:
![Fe_(+2) + O_(-2) = FeO](https://img.qammunity.org/2021/formulas/chemistry/middle-school/fog7pjo4yrgf5202g4bcu5jrsd5c4mns2o.png)
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