How old is earth compared to the other planets in the solar system?
About the same as the other planets - 4.5 Billion years.
According to the nebular hypothesis, all the planets in the solar system formed around this time 4.5 to 4.6 billon years ago, by the same process. Earth's final form may have delayed its final configuration by a few hundred million years, as a large porto-planet struck the embryonic Earth and caused the Moon to spin off. Venus may also have been struck by an early porto-planet as its axial rotation is the opposite to the rest of the planets and moons in the solar system.