a) AB||CD => ΔAOB ≈ ΔCOD => AO/OC=BO/OD=AB/CD
BO/OD=40/30
BO/OD=4/3 => BO=4OD/3
BO+OD=BD
4OD/3+OD=63
4OD+3OD=189
7OD=189
OD=27 cm
AO/OC=4/3 => AO=4OC/3
AO+OC=AC
4OC/3+OC=56
4OC+3OC=168
7OC=168
OC=24cm
b)AO=4·24/3=32 cm
BO=4·27/3=36 cm
PΔAOB=AO+OB+AB=32+36+40=68+40=108