Let x be the side length of the smaller square, in centimeters. Then the length of the larger square is (x+8) cm. The perimeter of the small square is 4x centimeters. The perimeter of the larger square is 4(x+8) cm. We are given the sum of the perimeters: 4x + 4(x+8) = 128 cm. Simplify and solve for x: 4x + 4x + 32 = 128 ====> 8x = 128 - 32 ====> 8x = 96 ====> x == 12. Answer. The side length of the smaller square is 12 cm. The side length of the larger square is 12+8 = 20 cm.