The radius of planet X is 5.0 bleems. It takes 4 earth years to complete it's orbit. Another planet, Z, orbits the same sun and has an orbit with the radius of 12 bleems.

Question

How long does it take for planet Z to complete an orbit?

Answer 1

kepplers third law: the square of the orbital period is proportional to the cube of mean radius.

4^2/T^2=5^3/12^3

solve for period T