How do I run calculations when users input numbers with commas?

I need for participants to enter three different numbers into text boxes. Then, later on, I want to add those numbers together and show the total to people. The problem is that if someone uses a comma in the text box, it gives an error and qualtrics can't calculate the total.

I have made sure that the text box validation requires a number, no text, but Qualtrics is still letting people enter "1,000" instead of "1000". In other words, Qualtrics recognizes "1,000" as a number for validation purposes, but when I try to add "1,000+1,000+1,000" in the background, it doesn't recognize these as numbers. What's the easiest way to fix this? It seems like a pretty major flaw to me that you can't run any calculations on user inputs if they happen to use a comma.