Jawabanmu

2014-05-24T07:41:09+07:00
Keliling = 80cm
2(p×l) = 80 cm
p×l = 40cm

p =  5/8 × 40 = 25 cm
l = 3/8 × 40 = 15 cm
L = p×l
L = 25 × 15
L = 375cm
2014-05-24T08:00:10+07:00
2(3x+5x) = 80 cm
16x = 80 cm
x = 5 cm
panjang = 5 x 5 = 25 cm
lebar = 3 x 5 = 15 cm 
Luas = pxl
15x25 cm
375 cm²
1 5 1