Folosim teorema lui Thales in triunghiurile EAB si EDC => EB/EC=EA/ED=AB/CD=12/20
Inlocuim datele cunoscute in fiecare raport
Notez EB=x si EA=y
=> x/x+12=12/20 => 20x=12x+144 => 8x=144 => x=EB=18
y/8+y=12/20 => 10y=48+6y => 4y=48 => y=12
Perimetrul =18+12+12=42