1. Wavelength:

* The distance between crests is the wavelength. In this case, the wavelength is 8 feet.

2. Frequency:

* Frequency is the number of waves passing a point in a given time. Here, 20 waves pass in 10 seconds.

* To find the frequency (waves per second), divide the number of waves by the time: 20 waves / 10 seconds = 2 waves/second (or 2 Hz).

3. Velocity:

* The velocity of a wave is calculated by multiplying the wavelength by the frequency:

* Velocity = Wavelength * Frequency

* Velocity = 8 feet * 2 waves/second

* Velocity = 16 feet/second

Therefore, the velocity of the wave is 16 feet per second.