‘Ummm, that is a problem, only one laptop and you both want it’ (said calmly) You might then ask your children what the answer to this problem is. If they don’t know, give them some guidance. If they agree to the solution you have found together and the problem is solved, praise them for their ‘good’ behaviour ‘Well done you worked it out, that was sensible.’
What have they learnt?
That when you have a disagreement with someone, the best thing to do is to talk about it calmly and try to come up with a solution or compromise. And you the parent have role modelled how to stay calm and treat people with respect, even if they are getting on your nerves.
So give this a try next time your children are arguing, be patient though, and consistent, just doing it once won't be enough, remember Rome wasn't built in a day.