Need help on math equation

I want to do some math equation in my app. Here is my query.

I got 2 data from firestore : 1. Total Tickets 2. Ticket Sold.

Here is how I show it :

I Use Progressbar to show progress of ticket sold.

I want below equation: % of total ticket sold / 100

I refer this document but it wont work for me. https://blog.flutterflow.io/math-expression-evaluator/

Please help me to do it.