Lisa memiliki sebuah balok yang berukuran panjang =(3x+2)cm dan lebar =(x+5)dan tinggi =(2x-4)cm jika jumblah panjang rusuk balik 156cm maka hitunglah luas perm

4 ( 3x+2+x+5+2x-4) = 156
3x+2+x+5+2x-4 = 39
6x+3 = 39
6x = 36
x = 6

p = 3x+2 = 3.6+2 = 20
l = x+5 = 6+5 = 11
t = 2x-4 = 2.6-4 = 8

luas permukaan = 2(p.l + p.t + l.t) = 2(20.11+20.8+11.8) = 2(220+160+88) = 2. 468 = 936 cm^2

156 = 4(3x + 2) + 4(x + 5) + 4(2x - 4)
156 = 12x + 8 + 4x + 20 + 8x - 16
156 = 24x + 12
156 - 12 = 24x
144/24 = x
x = 6

jadi :
p = (3*6 + 2) = 20
l = (6 + 5) = 11
t = (2*6 - 4) = 8

Luas permukaan = 2pl + 2pt + 2lt
= 440 + 320 + 176
= 936 cm^2