ANSWER
x = 9
Step-by-step explanation
We have the rectangle with width 3 ft and length (2 + x) ft.
The perimeter of the triangle is 28 ft.
The perimeter of a rectangle is given as:
P = 2(L + W)
where L = length
W = width
Therefore, we have that:
28 = 2[(2 + x) + 3]
28 = 2(2 + x + 3) = 2(x + 5)
28 = 2x + 10
=> 2x = 28 - 10 = 18
Divide through by 2:
2x/2 = 18/2
x = 9
That is the value of x.