Acertain radio wave has a frequency of 2.0x10^6 hz. what is its wavelength?

The wavelength of any wave is

                                           (wave speed) divided by (frequency) .

For electromagnetic waves, including radio, the
wave speed is close to  3 x 10⁸ m/s (the 'speed of light).

                Wavelength  =  (3 x 10⁸ m/sec) / (2 x 10⁶ /sec)

                                     =              150 meters  .