Number of comic books Bobbie has - b
95 = (9 + b) + b
Since 95 is the total number of comic books both boys have, it is equal to both boys' books added together. However, since we don't know how many books Kenny has, and only that he has 9 more than Bobbie, we can define that as (9 + b), or nine more than b. Then, we add b again, because (9 + b) is the number of books Kenny has, and if we add that to the number of books Bobbie has, it will equal the total of 95 comic books.