hope this helps i did this instead of my ap psych work haha
i didnt rlly check my answers so i hope this are correct <3
Since we know what one side is, there is another side equal to how that side looks like. So, the long sides are 16.5 + 16.5 = 33. Therefore, (39.4 - 33) / 2 will get you your answer.
I believe the answer would be 9.