to enclose the square lot, you need to have its perimeter.
the perimeter of a square is defined by the formula:
P = 4s
where P is the perimeter and s is the length of 1 side
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you are given that the length of 1 side is (5x-3).
Substituting you'll have:
P = 4 (5x-3)
P = 20x - 12
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Therefore you'll need (20x-12) meters of fencing materials
