i think you need spaces around the curly brackets.

The math operation should look like $e{ } with the math going between the brackets. This is explained here:

https://www.qualtrics.com/support/survey-platform/survey-module/editing-questions/piped-text/math-operations/#MathOperationsSyntax

So you would get $e{ value_1 + value_2 + … }

In your case, each value in the sum should be a text piping command for an embedded data item.

Here’s an example:

It is easy to make a mistake, since the syntax for a math operation looks similar to that of text piping commands, with just a small difference.

@Robbert I would recommend reading the support pages you've linked to. Especially the sections on Piped text and incorrectly formatted Piped text. 

If you mean $e{ value_1 + value_2 + … } is not correctly formatted, you are right, it is an example of a math operation, using placeholders. The parts “value_1” and "value_2” and “...” are to be replaced by actual piped text commands as in my example that follows it.

Thus the math operation for @BS86 would look like this:

$e{ ${e://Field/TotalBreakfast} + ${e://Field/TotalSnack1} + ${e://Field/TotalLunch} + ${e://Field/TotalSnack2} + ${e://Field/TotalDinner} + ${e://Field/TotalSnack3} }

I see now I made a mistake, as @ahmedA pointed out, in that when piped text is used in math operation, the ${ and } should be removed from the piped text. So it should be:

$e{ e://Field/TotalBreakfast + e://Field/TotalSnack1 + e://Field/TotalLunch + e://Field/TotalSnack2 + e://Field/TotalDinner + e://Field/TotalSnack3 }

Hi @BS86,

If that still does not work, consider doing this addition in the Data and Analysis section using a formula. This would be make sense if you do not want to display the sum to the respondent
 

https://www.qualtrics.com/support/survey-platform/data-and-analysis-module/data/add-new-fields/formula-variable-creation/#CreatingFormulas