Two car horns are sounded creating two sound waves with frequencies that differ by a factor of three. How does the speed of the higher frequency sound wave compare to the lower frequency sound wave?

Remains the same

Explanation:

The speed of waves of higher and lower frequency both will be same.

the speed of sound in a medium is constant and independent of it's frequency. Moreover, when the frequency changes wavelength changes accordingly, such that their product remains constant.

we know that

υ*λ = constant = velocity

υ = frequency

λ = wavelength.