I know it saves real numbers. I am having a hard time with remembering this one. When I have an expression, do i do the problem as if it where and int or do then promote the value? Or do i do the promotion right off the bat?
example.
double x;
x= 10 / 5 ;
its 2 but when its assigned to x its changes to 2.0? Is this right?

That is correct. If you had x = 1/2, the result of this integer division would be 0, and then be cast to the double value 0.0.