Answer:
360 sq feet
Explanation:
The width of the room is given in the question, 12 feet.
We don't know the length. Let's call the length x.
x = length
We were also given the perimeter, 81, that's the distance around the sides...
all the sides added up.
Use x for the long wall.
Use x-3 for the wall with the door in it.
x + 12 + x-3 + 12 = 81
combine like terms
2x + 21 = 81
subtract 21
2x = 60
divide by 2
x = 30
The room is 30 feet long by 12 feet wide.
Area =
length × width
= 30 × 12
= 360
The area of the room is 360sq feet.