Answer:
We know that for a rectangle of length L and width W, the perimeter is:
P = 2*L + 2*W.
In this case, we know that:
P = 85ft = 2*L + 2*W
L = 2*(x + 16)
W = (3*x - 1)
(where i guess that these units are in ft )
This is a system of equations:
Then we can replace the second and third equation into the first one, and get:
85 = 2*2*(x + 16) + 2*(3x - 1)
And solve this for x, we will get:
85 = 4x + 64 + 6x - 2
85 - 64 + 2 = (4 + 6)*x
23 = 10*x
23/10 = x
2.3 = x
Then the measures of the rectangle are:
L = 2*(x + 16) = 2*(2.3 + 16) = 36.6
W = (3*x - 1) = (3*2.3 - 1) = 5.9
The length of the rectangle is 36.6 feet, (and the width is 5.9 feet)