This is the concept of arithmetic, to get the number of comics each one get we proceed as follows;
number of comics Jerry has is 3y
number of comics Shaun has is 8
total number of comics they both have will be
total=8+3y
given that the comics have been divided equally between the two, each got:
(8+3y)/2 comics
simplifying the above we get:
=(4+3/2 )