What do you do about your children arguing and fighting?

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I have two girls age 9 and 10. All they do is argue and fight then want to get me involved. The only time I say something is when the hitting start. It really gets on my nerves. They argue from music to one looking at the other. Is this normal? I only had one of my siblings in the house with me growing up and we never went through this, maybe because he is a boy and nine years younger huh?