Answer:
b = 21 + 8a
Step-by-step explanation:
You have to get b on it's own therefore making b the subject.
You would use inverse operation so you would add both sides by 16a.
You would then be left with 2b = 42 + 16a.
You need b on it's own so you would divide each number by 2.
Thus, the answer would be b = 21 + 8a.
Hope this helps :)