Several problems heer...first=yu shood tell us the shape at the "thang"
sins yu sae leng & wide, me assume thang=rektangel
then yu sae area=64m...me suppose m is meters, & thats rong
it wood hafta be m^2
rim-leng=40, so half-rim=20=leng+wide
area=leng*wide=wide*(20-wide)=64
-wide^2 +20wide -64=0 or wide^2 -20 +64=0
wide=4 or 16...leng=16 & area=4*16=64