Carina buys a set of business checks from her bank. the checks cost her $26.73. she gives the teller $30.23. how much change should carina get back?

This is the concept of financial mathematics, the balance that Carina remained with after spending $26.73 to buy checks will be given by:
balance=Total amount-[Total cost of Checks]
Total amount=$30.23
Total cost of checks=$26.73
thus;
balance=30.23-26.73
=$3.5
the answer is $3.5