To calculate how much Rex and Renaye paid on average in addition to their $172.00 average minimum monthly payment, we need to first determine the total amount of their credit card debt. We can do this by taking the 18 monthly payments of $172.00 and multiplying them by 18:
$172.00 x 18 = $3,096.00
This means that Rex and Renaye paid $3,096.00 in minimum payments over the 18-month period. To determine how much they paid in addition to this amount, we subtract $3,096.00 from the total amount they paid, which is $4,120.00:
$4,120.00 - $3,096.00 = $1,024.00
Therefore, Rex and Renaye paid an additional $1,024.00 over the 18-month period. To determine how much, on average, they paid in addition to their $172.00 average minimum monthly payment, we divide $1,024.00 by 18:
$1,024.00 / 18 = $56.89
So, on average, Rex and Renaye paid an additional $56.89 per month in addition to their $172.00 minimum monthly payment.