[tex]l = \frac{4}{5} \times L[/tex]
[tex]a = L \times l = L \times L \times \frac{4}{5} [/tex]
[tex]80 = L \times L \times \frac{4}{5} [/tex]
[tex] {L}^{2} = 80 \times \frac{5}{4} = 100[/tex]
[tex]L = 10cm[/tex]
[tex]p = 2(l + L )=2 \times (8 + 10) = 2 \times 18 = 36[/tex]
[tex]l = \frac{4}{5} \times L = \frac{4}{5} \times 10 = 8cm[/tex]
