function CF_7Formula return Number is   --calculate percentage.
begin
  return((nvl(:sumpresent,0)/nvl(:sumwday,0))*100);
end;

Data:
stuid     Name        Percentage     Rank
1         ABC         87.50          want to calculate????
2         FAC         84.20          want to calculate????
3         DAC         85.78          want to calculate????
4         2AC         93.10          want to calculate????
5         HBC         94.58          want to calculate????
6         JA2         79.45          want to calculate????

SELECT  sno,to_char(mn,'MONTH-YYYY')  mm,stmn.class|| '  ' || stmn.section clss,
        ' '||stmn.name name,
        stmn.stuid,
        count(astuid) Absents
       ,substr(last_day(mn),1,2) Totaldays,studentid,wdays,DA
    from (select student.class, student.section,
              ' '||student.name name,
             student.stuid,studentid, da,mn 
from  (select trunc((last_day(dt) - trunc(dt,'iw') + 1) / 7) * 6 +
          least(mod(last_day(dt) - trunc(dt,'iw') + 1,7),6) -
least(dt - trunc(dt,'iw'),6)  da,add_months(TRUNC(to_Date(to_char(:yea,'DD-MON-YYYY'), 'DD/MM/YYYY')), rownum-1 ) mn
 from  (SELECT add_months(to_date(TO_CHAR(:yea,'DD-MON-YY'),'DD/MM/YYYY'),level - 1) dt
                 FROM dual CONNECT BY LEVEL < 13)),STUDENT
      where status='PRESENT') stmn,absent1,months
WHERE absent1.astuid(+)=stmn.stuid
and trunc(absent1.abdate(+), 'MON')=stmn.mn
and class=:cls
and section=:sec
and absent1.abdate(+)>=:yea
and to_char(mon,'MON')=to_char(mn,'MON')
and mon>=:yea
group by
sno,stmn.CLASS|| '  ' ||
stmn.SECTION, stmn.NAME, substr(last_day(mn),1,2) ,stmn.stuid,to_char(mn,'MONTH-YYYY'),to_char(mn,'MM'),studentid,wdays,da
order by sno,to_char(mn,'MM')

SELECT t.*, rownum FROM
(select pc,dense_rank() over (partition by stuid order by pc desc nulls last) as pos,stuid,class,section
from (select round((nvl(:sumpresent,0)/nvl(:sumwday,0))*100) As pc,stuid,class,section
       from student,absent1
       where student.stuid=absent1.astuid
      and student.stuid=:stuid
       and student.status='PRESENT'
       group by stuid,class,section)) t