How to do a format number with a sum?

Hello BI publisher Experts,

We are currently on 12.2.9 and have an open SR on this issue.

Long story short, how can we format a field to a number

TOTAL_AMOUNT is a string, but needs to be a number. It was previously a number

NONRECOVERABLE_TAX is a number

We want to do a sum of nonrecoverable tax and add total_amount; however we cant do that unless total_amount is formatted as a number.

We tried this but it didnt work

<?xdofx:to_number(TOTAL_AMOUNT+ sum(NONRECOVERABLE_TAX))?>

We also tried setting it as a variable and tried adding but that did not work either