Suppose your credit card has a balance of $ 8,400 and an annual interest rate of 15​%. You decide to pay off the balance over three years. If there are no further purchases charged to the​ card,

the monthly payment needed to pay off the balance over three years can be calculated using the formula for monthly loan payments:

P = [r* A] / [1 - (1 + r)^(-n)]

Where:
P = monthly payment
r = monthly interest rate (annual interest rate / 12 months)
A = balance on the credit card
n = number of months

First, we need to find the monthly interest rate:
r = 15% / 12 = 1.25%

Number of months = 3 years x 12 months = 36 months

Now we can plug these values into the formula:

P = [0.0125 * 8400] / [1 - (1 + 0.0125)^(-36)]
P = [105] / [1 - (1.0125)^(-36)]
P = 105 / 0.4497
P ≈ $233.40

Therefore, you would need to make monthly payments of approximately $233.40 to pay off the balance of $8,400 over three years with an annual interest rate of 15%.