we learn from the problem that the perimeter of the rectangle is equal to the perimeter of the square
so using the equation to find perimeter..
2(3x + 8) + 2(x - 1) = 2(x + 8) + 2(x + 8)
distribute all of the 2s
6x + 16 + 2x - 2 = 2x + 16 + 2x + 16
combine like terms on both sides
8x + 14 = 4x + 32
subtract 4x from both sides
4x + 14 = 32
and subtract 14 from both sides
4x = 18
divide each side by 4
x = 4.5
now plug this back into the perimeter equation for one of the shapes
rectangle: 8x + 14
substitute 4.5 in and solve
50 feet
now since both perimeters are the same, we can simply just multiply 50 by 2
answer: 100 feet
