On #243,
With respect to Carbon #2
it has H, Cl, COOH, and "R" as answer key denotes
Obviously you see Cl is #1 - highest molecular weight
#2 priority is R because there is a tie with the first atom directly attached to Carbon #2. One is C-O-OH and the R group is C-Cl-H
Cl beats O in molecular weight so #2 priority is R group here