How to calculate third virtual column value based on 2 virtual columns values in sub query

;with cte as (
select distinct s.S_ID,s.Name
  ,(select  cast(count(distinct A_Date)as float)from Attendance 
  where  a.C_ID=C_ID ) as Total_Classes,
  (select count(Pre) from Attendance where a.C_ID = C_ID 
  and a.S_ID = S_ID and Pre = 'True') as Attended 
  from Course c left outer join StudentCourse sc on c.C_ID = sc.C_ID 
  left outer join Student s on s.S_ID = sc.S_ID 
  left outer  join Attendance a on a.S_ID = s.S_ID and a.C_ID = c.C_ID where c.C_ID=6)
  select *,
  cast(Attended*100/nullif(Total_Classes,0) as decimal(10,2))  Percentage 
  from cte