They are both the same
1 millenium - 1000 yrs
1 century -100 yrs
100 x 10 - 1000yrs
Students= 613.6
Adults= 324.4
If 36x^3a+45xa^2=9a() then 9a is a factor the other factor, (), is the left side divided by 9a
(36x^3a+45xa^2)/(9a)
4x^3+5xa
So the () term is (4x^3+5xa)