Am nevoie repde de rezolvare completa!

DB=(Teorema lui Pitagora)=√(AD²+AB²)=√(8²+15²)=17
ΔDMN≈ΔBMA (un ghi unghi, alterne interne)⇒DM/BM=ND/AB=6/15=2/5⇒
DM/DB=DM/9Dm+MB)=2/(2+5)=2/7⇒MB/DB=5/7⇒MB=(5/7)*17=85/7 cm