Answer:
C
Explanation:
what is it you don't understand about this ?
the question only asks about a wallpaper border, which is a strip.
so, we don't need any areas, we only need the perimeter of the room.
that means we need to add up all sides.
the little "missing corner" on the top right would hurt us for the area of the room, but not for the perimeter.
just imagine, the room would be a perfect rectangle.
how long would the top side be ?
right, identical to the bottom side : 8 ft.
and how long would the right side be ?
right, identical to the left side : 4 yds.
now, look closely, did we lose (or add anything) of/to the side lengths by the missing corner up there ?
we lost area, but ... we did not lose perimeter distance !
i know, this sounds funny, but it is true. look again.
the short right side plus the long right side are together still the same length as the left side : 4 yds.
and the long top side and the shorter lower top side together are still the same length as the bottom line : 8 ft.
attention trap : the left and right sides are in yds.
1 yd = 3 ft !
so, long story short, the perimeter is as for a normal rectangle
2×length + 2×width = 2×8 + 2×4×3 = 16 + 8×3 = 40 ft
and the border costs $3 per ft, so we get
3×40 = $120
as the total price for the border.