When the user has the option of inputting their demographic, can they have more than one? Ideally, when dealing with a many-to-many relationship, you would use a composite key table. In very simple terms:
CREATE TABLE dbo.Answer (AnswerID int, UserID int);
CREATE TABLE dbo.Demographic (DemographicID int, DemographicDescription varchar(50));
GO
--Now your composite table
CREATE TABLE dbo.AnswerDemographic (AnswerID int, DemographicID int);
ALTER TABLE dbo.AnswerDemographic WITH CHECK ADD CONSTRAINT FK_AnswerID FOREIGN KEY (AnswerID)
REFERENCES dbo.Answer (AnswerID);

ALTER TABLE dbo.AnswerDemographic WITH CHECK ADD CONSTRAINT FK_DemographicID FOREIGN KEY (DemographicID)
REFERENCES Demographic (DemographicID);
GO

DROP TABLE dbo.Answer;
DROP TABLE dbo.Demographic;
GO
Is my understanding for that correct?

Then you could do a query along the lines of:
SELECT COUNT(A.AnswerID) AS Num,
       A.Answer
FROM dbo.Answer A
  JOIN dbo.AnswerDemographic AD ON A.AnswerID = AD.AnswerID
  JOIN dbo.Demographic D ON AD.DemographicID = D.DemographicID
WHERE A.QuestionID = 1
AND D.DemographicDescription = 'Sales Department';

So you can easily count the answers for specific demographics, and people answering can give all their demographic details, instead of having to choose only one, when many might apply.