Please check below example:
declare @Results table (
Id int not null,
Answer int not null,
NoOfComments int not null
)
insert into @Results (Id,Answer,NoOfComments) values
(18, 1, 2),
(19, 2, 0),
(20, 3, 0),
(21, 4, 0),
(22, 5, 1)
select *,((NoOfComments * 100.0) / SUM(NoOfComments) OVER (PARTITION BY (1))) as Pcnt
from @Results
* This is only example not a stored procedure