Yes, I can help answer your homework question.
To find the frequency of the wave, we need to use the formula:
Frequency (f) = Number of waves / Time
Given that twelve waves pass an observer in four seconds, we can substitute these values into the formula:
Frequency (f) = 12 waves / 4 seconds
Frequency (f) = 3 waves/second
So, the frequency of the wave is 3 waves per second.
Please note that the wavelength and amplitude provided in the question are not necessary for calculating the frequency in this particular case. The frequency is determined solely by the number of waves passing the observer in a given time interval.