If a small planet were located 7 times as far as the Earth's distance from the Sun, it period is ___ earth years?

Answer 1

Use Kepler's third law.
(Period,y)^2/(Distance,a.u.)^3 = 1
(for objects orbiting the sun)
The distance is 7 a.u in this case.

(Period,y)^2 = 7^3 = 343
Period = 18.5 years