Answer:
The longer length is 35ft
Explanation:
Given


Required
Determine the longer length
Represent the length with L and width with W
So, we have:
--- Area
--- Perimeter
Divide both sides by 2 in:


Make L the subject:

Substitute 51 - W for L in



Reorder the equation

Expand



Split:


This implies that the longer length is 35ft