Have a project request guidance

i have a project i m trying to do i need help the project is as follows
its a ticketing system
rfid card is initially loaded with a value eg 20

when the card is tagged if stored value more than 0 then green light and subtract 1 from the 20
and also print the remaining balance

What have you tried? What was the result? We can help you with your code, but can’t write it for you.

Read the how to use this forum sticky to see how to post code and some advice on how get the most from the forum.

And hope your customers don’t have a RFID writing device so they Change their own 1 to 100…