Worth repeating this elementary math used in concession stands all across the USA.
It’s easy to teach a cashier how to count out the correct change. Says the sales is $3.73 and the customer hands over a $20.00 ->
put the $20 on top of the register -> say 3.73
take out 2 cents ->say 3 75
take out a quarter -> say 4
take out a dollar -> say 5
take out a 5 -> say 10
take out a ten -> say 20
and then hand all that to the customer.
Easy Peases.
Maybe teaching the understanding that you can solve a subtraction problem with addition is the breakthrough...