Answer:
The missing side would be 6.
And the area would be 54.
Explanation:
The perimeter equals 30, that's the outside of the rectangle. They give you a part of the perimeter, 9ft. So 9ft and there's another 9ft on the bottom line, (because it is equal to the top width) Which equals 18. To get the other sides you need to subtract 18 from the whole perimeter, 30. Which gives you 12. And there's two sides left, so divide by 2, and you have 6 on each side(left and right sides) Perimeter is adding all the sides up.
And the Area formula is Area=Length times Width. Area=9ft×6ft Which equals 54.