Answer: the length if the three sides are 31 feet, 23 feet and 18 feet.
Step-by-step explanation:
Let x represent the length of the shortest side of the triangle.
Let y represent the length of the second side of the triangle.
Let z represent the length of the third side of the triangle.
The second side of a triangular deck is 5 feet longer than the shortest side. This means that
y = x + 5
The third side is 5 feet shorter than twice the length of the shortest side. This means that
z = 2x - 5
If the perimeter of the deck is 72 feet, it means that
x + x + 5 + 2x - 5 = 72
4x = 72
x = 72/4 = 18
z = 2x - 5 = 2 × 18 - 5
z = 36 - 5
z = 31
y = x + 5 = 18 + 5
y = 23