To solve this problem we will use Kepler's third law, which tells us that the square of the orbital period of a planet is differently proportional to the cube of the average distance from the planet to the sun, mathematically that is,
[tex]P^2 = a^3[/tex]
Here,
P = Period
a = Average distance
If we rearrange the equation to find the average distance we have that
[tex]a = P^{ \frac{2}{3}}[/tex]
Replacing the period given of 8 years we have that
[tex]a = 8^{ \frac{2}{3}}[/tex]
[tex]a = 4 AU[/tex]
Therefore the average distance of the asteroid from the Sun is 4 Astronomical Units