With 7 children we get disagreements on a daily basis. Resolving the disagreements can be challenging, especially if no-one wants to give anything. A method that works for us, when we remember to use it, goes as follows:
I'm guilty of this far too often. Especially at the end of the day. Usually when I'm trying to get out the door to get to some event, when chores need doing or when the children are screaming bloody murder because their toast was cut wrong. Someone is fussing, someone else asks for something and gets impatient and starts screaming, then I respond louder so that I can be heard, then it gets louder and louder, then other kids join in. Unfortunately, the kids copy what they see me doing so it's a never ending cycle.