Armando has a previous balance of $1,537 on a credit card with a 23.4% APR compounded monthly. If he made a payment of $84 this month, what is the new balance on his credit card?

When you don't pay off your credit card then you pay the previous months interest - ouch! The interest is Prt

Current balance = Previous balance + Interest - payment

Current balance = 1537 + (1537) (23.4/100) (1/12) - (84)

Current balance = $1482.97