What are oxidation numbers and how do they work?
What have you tried to understand about it? Googling the term 'oxidation number' seems like a good start. The first hit will give you an overplus of information.
Yeah, googling it would give you what you need.
Also, if ever in need of a way to remember it during a test (believe me, been there done that) just remember that
"oxidation is increase in oxidation number and reduction is decrease (well, reduction obviously:P) in oxidation number"
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