Your iclicker operates at a frequency of approximately 900 mhz (900x106 hz). what is the approximate wavelength of the em wave produced by your iclicker

The clicker emits EM (electromagnetic) wave which travels at the speed of light, that is
v = 3 x 10⁸ m/s

The frequency is
f = 900mHz = 9 x 10⁸ Hz

Because velocity = frequency * wavelength, the wavelength, λ,  is given by
fλ = v
λ = v/f
   = (3 x 10⁸ m/s) / (9 x 10⁸ 1/s)
   = 1/3 m

  1/3 m

Depotion can i think