Which gets triggered first

Hello team,

I am updating some fields from entity A to entity B. ( I created a workflow  when entity A is selected  from Entity B through lookup , I am updating some field from entity A to Entity B) when entity B  record is created, records status changes

Now I want to make sone fields read only in entity B using business rule once the values are updated  from entity A

I am not sure which gets triggered  first.

Any help or guidance is highly appreciated.

Thanks