pentru usurinta in scriere notam:
AM = BN = x
BM = 10-x
NC=8-x
AP=x unde NP o ducem perpendiculara pe AD, P ∈ AD
x=6
aria ABCD = 10 x 8 = 80
aria MBN = x(10-x)/2 = 12
aria AMN = aria ABNP/2 = 10x / 2
aria AMN = 30
aria DMN = aria ABCD - aria MBN - aria AMD - aria NCD
aria DMN = 80 - (12 + 24 + 10)
aria DMN = 34