Hi smile,
Check the below modified query.
SQL
declare @StdID varchar(50)
Set @StdID= 'R-0003'
select * into #TempMarks
from ( 
select *
from ( 
	select [SubjectID],[SetExamID],[Marks]
	from tblSetMarks
	where AdmissionNo= @StdID
	)
	as tbl 
pivot (sum(Marks) for [SetExamID] in ([14],[15])
) as PVT
) as s
select CONVERT(VARCHAR(20),SubjectID) SubjectID,[14],[15],[14]+[15] as 'Grand Total' from #TempMarks
union all
select 'Total', sum([14]), sum ([15]), sum ([14]+[15]) from #TempMarks
drop table #TempMarks
Output
| SubjectID | 14 | 15 | Grand Total | 
| 12 | 21 | 29 | 50 | 
| Total | 21 | 29 | 50 |