The perimeter of anything is the sum of the measures of all of the sides. The difficulty with the way you stated the problem is that your perimeter could be just about anything larger than 24 inches. That is because you didn't specify the units on your "9" measurement. Is it 9 light years or 9 nanometers? Just because the other two measurements are in inches doesn't necessarily guarantee anything about the third one. Be that as it may, I wouldn't have done the arithmetic for you anyway, so you really didn't lose anything.
John
My calculator said it, I believe it, that settles it
