Like for everything else in physics there is an equation for waves. The equation is velocity= frequency times the wavelength. Velocity is determined by the medium (speed), which means that the medium determines how fast or slow the wave is. If frequency increases wavelength decreases, they have an inverse relationship. Meaning that if one goes up the other one goes down. Frequency is measured in hertz, velocity is measured in meters per second, and wavelength is measured in meters. If you were given a problem where it says that the frequency of a wave is 10 hertz and the wavelength was 2 meters, to find the speed you would multiply the frequency and wavelength together resulting in 20 meters per second. If you were asked to find the frequency of a wave and you were given the velocity and wavelength you would divide velocity and wavelength.