Maintain the area of a polygon when offsetting one side

Question

I have an irregular polygon with the a specific area (area_red). How can I get the (parallel) offset value (y) of n selected sides in order to maintain the same area (area _red = area_green) when (parallel) offsetting one side by x?

Answer 1

...Okay, I guess I will simply loop trough the offsets constanstly and check each time if the area is the same. lol.

Answer 2

it seems that is the way to do it

something like this: https://edgnyc-my.sharepoint.com/:u:/p/wwang/EUHEhzrl1KBFsIx8YFNtTb8BrBHw55PFOJH5NqbIcQ9vzw?e=EvMyVa