Theres no picture so I can’t rlly solve it
For this case we have the following variables:
P = area covered by a roll of wallpaper
w = the total area of the walls
n = number of rolls to buy
We write the equation for n.
You must take into account that you can determine this amount by dividing the total area between the area covered by each roll of paper.
We have then:
Answer:
a formula that will help them determine how much wall paper they'll need to purchase is:

7a)
x - 10 + x - 11 + 3x + 6 = 180
5x -15 = 180
5x = 195
x = 39
7b)
y = 3x + 6
y = 3(39) +6
y = 117 + 6
y = 123
I think that the answer could be D