self join introduces errors in count

[joeblow2]

I've included my tables, input data, output data and sql.
As you will notice the self join introduces errors in numbers in both Expr1 and Expr3.

I hope someone can see what is introducing the errors and how to fix it.
Thanks

 

[joeblow2]

What I am doing is trying to get a combined solution set.
Basically I want to combine the results of these two queries:
Select Event_id,Question_id,Response,AgeGroup,Sum(Quantity)
From Event_line
Group by Event_id,Question_id,Response,AgeGroup
and
Select AgeGroup, Sum(Quantity)
From Event_line
Group by AgeGroup

individually run they give the correct result, however when combined by using a self-join,
I am getting double counting. See my attached Word document to see what I am getting as opposed to the desired result.