Answer:
Length = 12 ft, she should buy 160 ft. of wallpaper border
Explanation:
In order to find perimeter, you have to add up the values of all of the sides. Assuming that Addilyn's bedroom is a rectangle, we can use this equation to find the length:
8 + 8 + l + l = 40
Combine like terms
16 + 2l = 40
subtract 16 from both sides to isolate the 2l
2l = 24
Divide both sides by 2 to isolate the l
l = 12
The length of her room is twelve feet.
If she wants to put the border around the room four times, that means we'll have to multiply the perimeter by 4 to find out what length of wallpaper border she should buy.
4 * 40 = 160
She should buy 160 ft of wallpaper border.