BB bunny = 7 carrots
Bo Bunny = 5 + BB bunny which is 5 + 7 (being that BB Bunny has 7).
So now we know that BB bunny has 7 and Bo bunny has 12.
Billy bunny = Bo bunny - 3 which is 12 - 3 (being that Bo bunny has 12)
So now...
Billy bunny has 9, Bo bunny has 12 and BB bunny has 5
Add them together and 9 + 12 + 7 = 28 total carrots!