To do this problem, you need to first get rid of all the parenthesis. Since all the operations are addition (+), remember the Associative Property of Addition. This property says when you're adding, it doesn't matter where you put the parentheses because it'll all add up to the same thing.
That means (3b + 2r) + (4b + r) = (3b + 4b) + (2r + r), or even, just get rid of the paratheses in general and have (3b + 2r) + (4b + r) = (3b + 2r + 4b + r).
Either way, now you can add like terms so:
(3b + 2r) + (4b + r) = (3b + 4b) + (2r + r) = 7b + 3r
Your answer is B) 7b + 3r
