Tom's statement shows a previous balance of $2452.64, a payment of $160, and new transactions $138. what is his new balance if his apr is 15.6%?

marco's unpaid credit card balance is $4332.75. his apr is 18.6% what is his new balance if he made one new transaction of $432?

Tom:
Previous balance: 2,452.64
payment: 160
new transaction: 138
APR: 15.6%

We need to divide APR by 12 to get the monthly rate: 15.6% / 12 = 1.3%

2,452.64 - 160 = 2,292.64 
2,292.64 * 1.3% = 29.80  interest for the month. We did not include 138 because it still is within the 1 month period and it is not subject to interest. Only the revolving amount of 2,292.64 has interest.
2,292.64 + 29.80 + 138 = 2,460.44 NEW BALANCE OF TOM

Marco:
Unpaid credit card balance: 4,332.75
APR: 18.6% 
New transaction: 432

Divide APR by 12 to get the monthly rate: 18.6% / 12 = 1.55%
4,332.75 * 1.55% = 67.16
4,332.75 + 67.16 + 432 = 4,831.91 NEW BALANCE OF MARCO