13b + 9b + 3bk - 7bk - 4bk=?
To do this, you must combine like terms. Combine the ones in which ALL variables are the same. So b goes with b, and bk goes with bk.13b+9b=22b3bk-7bk-4bk=-8bkSo your final answer is 22b-8bk:) -Kibeye