First you want to divide the perimeter by 2
Then you should consider numbers that sum to half the perimeter but multiply to the largest area
P = 110 = 2L + 2W
Divide both sides of the equation by 2
55 = L + W
What numbers sum to 55 and multiply to the largest area
For example
20 + 35 = 55
20 x 35 = 700
21.5 + 33.5 = 55
21.5 x 33.5 = 720.25
Give it a try see if you can come up with larger areas than 756 that fit the criteria there are a few.