Wavelength of any wave = (speed) / (frequency)
Speed of light = 300,000,000 m/sec
Wavelength = 3 x 10 to the 8 / 750 x 10 to the 12 = 4 x 10 to the -7 or 400 nanometers.
239.583 days is the answer
It goes sun moon earth the moon is blocking us from seeing the sun.
Answer:
Lever => 
Pulley => G = M x n (gravitational acceleration)
Wheel and axle => M.A = Radius of the wheel/radius of the axle = R/r
Inclined plane => It can be divided into two components: Fi = Fg * sinθ - parallel to inclined plane. Fn = Fg * cosθ - perpendicular one.