I am trying out operations on sets and i have become stuck on how you could update set of pairs, say I have a set $A$: $$A = \{(a,3),(b,5),(c,7)\}.$$
If I wanted to add a pair I would use the union of the two sets; $$A \cup \{(x,8)\}.$$ Or remove one I would use the set difference; $$A \setminus \{(b,5)\}$$ How do you go about updating $a$, $b$ in the pair $(a,b)$ in set $A$?