[tex]\displaystyle\\
P = 312~m\\
L + l + L + l =312~m\\
2(L + l)= 312~m\\\\
l = \frac{1}{2} \times L = \frac{L}{2}\\\\
2\Big(L + \frac{L}{2} \Big)= 312~m\\\\
2L + 2\times \frac{L}{2} = 312~m\\\\
2L + L = 312~m\\\\
3L = 312~m\\\\
L = \frac{312~m}{3} = \boxed{104~m}\\\\
l = \frac{L}{2} = \frac{104~m}{2} =\boxed{52~m} \\\\
\text{Verificare:}\\\\
P = 2L + 2l = 2\times 104 + 2\times 52 = 208 + 104 = \underline{\bold{312 ~m}}
[/tex]
