Zack is preparing for a marathon and currently weighs 162 pounds. His total body weight can be expressed as 3x^3 + 9x^2, and his body fat weight can be expressed as 3/2x^2. Write a function which represent Zack's body fat percentage.
Fat percentage = Fat weight / Body weight * 100
Assuming that 3/2x^2 is (3/2)x^2
Fat percentage = \(\frac{3x^3+9x^2}{ \frac{3}{2} x^2} 100= [2x+6]100 = 200x+600\)