18a-14 Would be your answer because you are basically distributing which is taking the number on the out side of the parenthesis and multiplying it by all the numbers inside of the parenthesis
You would times 2 by 9a because 9a-7 is in parenthesis and when it’s in parenthesis you do it first then you times 2 by -7 and get -14. Now you have 18a-14
