Step-by-step explanation:
I assume this is a rectangular shape (all the angles are 90°). so, this is kind of a large rectangle with one corner "folded in". it still has the same perimeter as the rectangle without the folded corner, as the inward folded sides complement the remaining outside sides to have the same lengths as the full length and width sides.
also you must have skipped some information about the pool. see c) for more information.
a)
the missing vertical side is
(12 - x) - (3x - 3) = 12 - x - 3x + 3 = 15 - 4x
the missing horizontal side is
(5x - 2) - (4x - 6) = 5x - 2 - 4x + 6 = x + 4
b)
the full perimeter is the sum of all sides
(12-x)+(5x-2)+(3x-3)+(4x-6)+(15-4x)+(x+4)
which is the same as
2×(12-x) + 2×(5x-2) = 24 - 2x + 10x - 4 = 8x + 20
c)
tricky, as we did not get any absolute constraint or reference at all. no ratio of the side lengths like length/width. nothing.
x could be any number, and it would all still fit relatively.
so, to have the chance to say something, I assume that the full length and full width of the pool are the same.
12 - x = 5x - 2
14 - x = 5x
14 = 6x
x = 14/6 = 7/3
so, every side would be
5×7/3 - 2 = 35/3 - 6/3 = 29/3 ft = 9 2/3 ft
d)
5x - 2 = 5×7/3 - 2 = 29/3 ft
12 - x = 12 - 7/3 = 36/3 - 7/3 = 29/3 ft
3x - 3 = 3×7/3 - 3 = 7 - 3 = 4 ft
15 - 4x = 15 - 4×7/3 = 45/3 - 28/3 = 17/3 ft
4x - 6 = 4×7/3 - 6 = 28/3 - 18/3 = 10/3 ft
x + 4 = 7/3 + 12/3 = 19/3 ft
the full perimeter is
8x + 20 = 8×7/3 + 60/3 = 56/3 + 60/3 = 116/3 ft
$3.47 per ft means the whole fence costs
116/3 × 3.47 = $134.1733333... ≈ $134.17
