[tex]\text{Voi nota cu L lungimea, l latimea si cu h inaltimea.Stim ca diagonala}\\
\text{unui paralelipiped dreptunghic are formula:}\\
\boxed{d=\sqrt{l^2+L^2+h^2}}\\
\text{Deci: }\sqrt{l^2+L^2+h^2}=13|()^2\\
~~~~~~~~~~~l^2+L^2+h^2=169\\
\text{Mai stim ca :}\\
L+l+h=19\ |()^2\\
(L+l+h)^2=361\\
L^2+l^2+h^2+2(L\cdot l+L\cdot h+l\cdot h)=361\\
169+A_t=361\\
\boxed{A_t=192\ cm^2}[/tex]
