The average distance between Earth and the sun is 1.50e8 km.
Calculate the average speed, in km/h, of Earth assuming a circular path about the sun. Use the equations v = 2(pi)r/T.
You know that, for the Earth, T = 365.25 days. Convert that to hours (by multiplying by 24 h/day) and then use the formula given. You will get the velocity in km/h