the area for a regular decagon is a bit complicated to type out, but a quick google search "decagon formula" should bring it up.
its like A= (5/2) a^2 sqrt(5+2*sqrt(5)) so yeah just google that and plug the values that they gave you in
i got 1107.97~
the perimeter is P = 10a where a is the side length. in this case it is 12. so the perimeter is 10*(12) which is 120cm.
