If there is a person on another planet, and his year is 80 Earth's years, how far would his planet have to be from the Sun?

Here you GO * * * Uranus takes 84 years to orbit the sun it is 2,870,972,200 km from the sun or 1,783,939, miles.

@Tropical_Willie So, it would have to be a bit closer than Uranus, but somewhere in that distance. Thanks.

Here is a helpful site if you want to know the math
http://www.physicsclassroom.com/class/circles/Lesson-4/Mathematics-of-Satellite-Motion

@Rarebear AAAAAH math! [runs away]

Kidding, thanks for the link.

Note that the distance between the star and the planet is not the only relevant variable. The mass of the star and the planet also affect the period of revolution.

@Zissou Actually the mass of the satellite is irrelevant. See my math link above and scroll down to the orbital speed equation.

Search me, I’m still trying to wrap my mind around the Alien Autopsy.

@Rarebear. Mass is absolutely relevant.

@filmfann The mass of the central body, yes.

The formula: velocity of orbit = sqrt(G*Mcentral)/R)