The wavelength of a wave is defined as the distance between successive points of the same phase in the wave (such as crest to crest or trough to trough).
In this case, you are given a separation of 6 meters between points A and B, but we need to know how many complete cycles fit into that distance to calculate the wavelength.
Since the problem doesn't provide information on the number of cycles between points A and B, if we assume that A and B represent the distance of one full cycle, then the wavelength would be equal to the distance, which is 6 meters.
Thus, the answer to the question, assuming A and B cover one complete cycle, would be:
6 m