Question

The balance on Taylor's credit card is $2000. It has an interest rate of 12.5%. She wants to compare the difference between paying $75 and $100 of the monthly balance. How much does she save in interest and fees if she pays $100 instead of $75?

Answer 1

A credit card interest rate of 12.5% ?
Time for your school board to get new textbooks.

Anyway...
case 1: payment is $75
interest on 2000 = .125/12*2000 = $20.83
so the actual repayment on the balance = 75-20.83 = $54.17
balance = 1945.83
interest in the next month = $20.27

case 2: payment is $100
interest on 2000 is still $20.83
repayment = $79.73
balance = 1920.27

interest in the next month = 20.01

so she saved 82 cents in the interest the month after

Notice we had to take a look at the 2nd month to see any effect.

(pay off ALL of it!!!!)