I honestly haven't been on in a while, a couple of years in fact. The people here remained kind and friendly but the things that were immediately noticeable after 2-3yrs was the quality of questions on the website, it's not fair. Also, this site definitely has the potential to grow bigger and expand to help more people but I don't know what's up with the direction it's taking...
Simply meaning, two numbers that multiply to give 180 and add (x2 due to 4 sides) to give 54.
\(\\X ⋅ Y\\ \\X+X+Y+Y\\ \)
Factors of 180:
Numbers have to be below 54 itself to add up to it
Find two factors that multiply to 180 that add to 54 (all 4 sides)
12 and 15
Length must be 15ft
By diagonal, I assume you mean a diagonal line intersecting through the rectangle (unless you only mean the length of the patio itself).
When squared that would be 369ft.