Question

Gary's unpaid credit card balance is 2543.32. His APR is 17.4%, and he made one new translation for 320

Answer 1

New balance = unpaid balance + periodic interest of unpaid balance + new transaction
Periodic interest rate = APR/12
                                  = 17.4%/12
                                  = 1.45%
unpaid credit card balance = 2543.32
new transaction = 320
New balance = 2543.32+(0.0145 x 2543.32) +320
New balance credit card balance  = 2900.19814