Question

What is the orbital radius of venus if venus has an average orbital period of 0.615 years

Answer 1

T^2 = a^3 if by "average radius" you mean semi-major axis in AU and T is in Earth years. 

Jupiter: 5.2^3 = 140.608, 140.608^0.5 = 11.86 
Venus: 0.723^3 = 0.37793, 0.37793^0.5 = 0.615 years = 224.5 days