Math
posted by Mary .
the time x (in days), that it takes a planet to revolve around the sun can be approximated by the equation x=0.407√(d^3),where d is the mean distance of the planet from the sun in millions of miles. It takes Venus approximately 226 days to complete one revolution of the sun. To the nearest million miles, what is the mean distance of Venus from the sun?

Just use the formula provided.
226 = 0.407*d^(3/2)
555.3 = d^(3/2)
555.3^(2/3) = d
d = 67.56 (million miles)
That rounds to 68.