Answer:
The frequency of a wave is the number of cycles per unit of time. In this case, the number of cycles or wave crests is 60, and the time is 15 seconds.
To find the frequency, we can use the formula:
frequency = cycles / time
Substituting the values, we get:
frequency = 60 / 15
frequency = 4 cycles/second or 4 Hertz (Hz)
Therefore, the frequency is 4 Hz.