How to sync target temperate across different items

Setup, Configuration and Use Beginners
1

Dear all,

I have a nest thermostat , homekit thermostat and a physical air conditioner, all of them have an item of “target temperature” in openhab. What is the best way to update the other two values if one update? (ie A -> BC, B->AC, C->AB)
Thanks.

2

Can you post your items, please?
Have you tried to write a rule?