Answer:
2x+18
Explanation:
this is a rectangular prism which will mean their are four sides (two pairs perpendicular to each other) so we can automatically assume the width (9) can be multiplied by 2 which gives you 18. If the length is x then we know we have to do the same thing and multiply 2 by x but since we don't know the exact amount we can just keep it at 2*x which is the same as 2x.
We are not finding the answer but we are looking for the math problem so this will give you the answer: 2x+18