It would simply be "They respect each other".
Respect in time tenses is either spelled, "Respected", "Respect", or "Will Respect."
The fact that it's third person does not change the word since it can be said as "I respect you", "You respect yourself" "They respect each other"
A- n-1
if its 1 fewer then a number, that means a number - 1, so n-1
What is it they you are trying to say.