Answer: 125 ft.
Explanation:
Assuming the perimeter of the park is 400 ft, the equation can be represented as
2l + 2w = 400
Since we know that the width is 50 ft shorter than the length, using algebra, you replace the variable w, with
2l + 2(l-50) = 400
Then, solve for variable l, or length
2l +2l - 100 = 400
4l = 500
l = 125
Now, plug in l and solve for w
2(125) + 2w = 400
250 + 2w = 400
2w = 150
w = 75
2(125) + 2(75) = 400
250+150 = 400
400=400
l = 125, w = 75
So the length is 125 ft