panjanf suatu persegi pnjg adlh 3cm kurangnya dari 2kali lebarnya.jika kllnya sama dengan 54cm,maka luasnya adalah

K = 54
p = 2x-3
l = x

2(2x-3)+2(x) = K
4x-6+2x = 54
6x-6 = 54
6x = 54-6
x = 48/6 = 8

p = 2x-3 = (2*8)-3 = 16-3 = 13
l = 2x = (2*8) = 16

L = p*l = 13*16 = 208

Diketahui :
p = (2l - 3) cm
K = 54 cm

Ditanya : L ?

Dijawab :
Keliling = 54
2p + 2l = 54
2 (2l - 3) + 2l = 54
4l - 6 + 2l = 54
6l - 6 = 54
6l = 54 + 6
6l = 60
l = 60/6
l = 10 cm

p = 2l - 3
p = 2 (10) - 3
p = 20 - 3
p = 17 cm

Luas persegi panjang
= p x l
= 17 x 10
= 170 cm²