tolong bantu saya mengerjakan soal nmr 14 ini,,please

Keliling Persegi Panjang = 80 cm
Keliling = 2 ( l + P )
80 = 2[(12 + l) + l]
80 = 2[12 + 2l]
12 + 2l = 
12 + 2l = 40
2l = 40 - 12
2l = 28
l = 14 cm 
l = 14

Pjg = x
Lbr = x-12 .. soal nya diket selisih p dan l adalah 12

K = 2 ( p+l)
80 = 2 ( x + x-12)
80 = 2 (2x -12)
80 = 4x - 24
104 = 4x
26 = x
Jadi, p = x = 26
L = x-12 = 26-12 = 14

Luas = p x l
= 26 x 14
= 364