Jawabanmu

2014-04-28T01:20:44+07:00
Lebar (l) = x
Panjang (p) =  \frac{7x}{6}

K = 2 (p+l)
78 = 2 ( \frac{7x}{6} + x)
78 = 2 ( \frac{13x}{6} )
78 =  \frac{26x}{6}
78 x 6 = 26x
468 ÷ 6 = 26x
18 = x

Jadi, lebar = 18 cm
       Panjang =  \frac{7}{6} × 18 = 21 cm