Jawabanmu

2014-05-19T08:28:22+07:00
P = 3+l atau 3+x
l = x

k = 2p + 2l
30 = 2 × (3+x) + 2x
30 = 6 + 2x + 2x
30 = 6 + 4x 
30 - 6 = 4x
   24   = 4x
    x    = 24 : 4 = 6

p = 3 + x
p = 3 + 6 = 18 cm
l = 6 cm

L = p×l
L = 18 × 6 = 108 cm²


Maaf kalau ada kesalahan
2014-05-19T08:44:59+07:00
Diket.: l = x
         p = 3+x
         k = 30
ditanya : Luas?
K : 2(p+l)
30= 2[{3+x} + {x}]
30=6+2x+2x
30=6+4x
30-6=4x
24=4x
6=x 
jadi: p=  3+6=9
       l  = 6
L = p x l
       9 x6 =54cm²