In[]:=
Regions={(*{{0,1200},{636,0},{0,0},{0,1200}},*){{0,1666.66666666666666667},{2500,0},{0,0},{0,1666.66666666666666667}},{{0,1350},{1800,0},{0,0},{0,1350}},{{0,1500},{1000,0},{0,0},{0,1500}},{{0,2250},{900,0},{0,0},{0,2250}}};reg=Region/@Polygon/@%;RegionIntersection[reg];{AppendTo[reg,%]//RegionPlot[#,AspectRatioAutomatic,ImageSizeMedium,PlotTheme"Dark"]&,%//RegionPlot[#,AspectRatioAutomatic,ImageSizeMedium]&,StringRiffle [{"Area=",Area[%],"square units"}]}RegionBoundary[%%]//Normal//InputForm//ToString//StringSplit[#,{"[","]"}][[2]]&
Out[]=
,
,Area= 716250 square units
Out[]=
{{0, 0}, {0, 1350}, {200, 1200}, {750, 375}, {900, 0}, {0, 0}}