Daca AB=3/4 x AC
AB= 9 cm
3/4xAC=9
AC=9x4/3=3x4=12
A-B-C coliniare deci AC=AB+BC
12=9+BC
BC=3
MN=BM+BN
BM=AB :2
BM=3,5 CM
BN=1,5 CM
MN=5 CM
