I need help with this ATM transaction code I'm writing.

Question

I'm writing an ATM transaction code, i have an initial balance, how can i minus the amount withdraw from the initial balance and display it on the check account balance
https://code.sololearn.com/cW5XzGxOOGl3/?ref=app

Answer 1

What about considering this amount as an instance variable (atribute in other programming languages) you'll be able to modify ?