Răspuns :
[tex]\it DE||BC,\ din\ teorema\ fundamental\breve{a}\ a\ asem\breve{a}n\breve{a}rii\ \Rightarrow\ \Delta ADE \sim \Delta ABC\\ \\ \dfrac{AD}{AB}=\dfrac{6}{9}=\dfrac{2}{3}\ (raportul\ \ de\ \ asem\breve{a}nare)\\ \\ \\ DE=\dfrac{2}{3}\cdot BC=\dfrac{2}{3}\cdot 15=10cm\\ \\ \\ AE=\dfrac{2}{3}\cdot AC=\dfrac{2}{3}\cdot 18=12cm[/tex]
[tex]\it \mathcal{P}_{ADE}=AD+DE+AE=6+10+12=28\ cm[/tex]