Answer:
A = 2 cm ,  λ = 8 cm
Explanation:
The amplitude of a wave is the maximum height it has, in this case the height is measured by the vertical ruler,
We are told the balance point is in the reading of 5 cm, that the maximum reading is 3 cm and the Minimum reading is 7 cm. Therefore, the distance from the ends of the ridge to the point of equilibrium is
     d = 7-5 = 2 cm
     d = 5-3 = 2 cm
     A = 2 cm
The wavelength is the minimum horizontal distance for which the wave is repeated, that is measured by the horizontal ruler.
The initial reading for 4 cm and the final reading for 8 cm, this distance corresponds to a crest of the wave, the complete wave is formed by two crests whereby the wavelength is twice this value
     Δx = 8-4 = 4 cm
     λ = 2 Δx
     λ = 8 cm